Until everyone starts treating 5/10 as average, and not below average, numbers will be pretty meaningless.
I can abide by a 5/5 numbering system though. Now that I think of it, here's something I wrote awhile back about how a game can be described and judged under a 5/5 rating system. It's...er...quite long, so I'll stick it in a spoiler tag if anybody is interested in reading it.
Visuals
Visuals are discussed in two ways. Graphical power and art direction. A game can be fantastic visually with potent graphical power alone, but can also make up for merely functional graphical power with a unique and appropriate art direction. The goal of a games visuals are entirely dependent on the type of game, but the usual goal should be the depiction of a world. A game world, whether our world or a fantasy world, should be believable. A good game world will avoid the feeling that it is just a game world. To do this a game needs a culmination of good-looking (though not necessarily realistic) visuals, convincing character models and strong animation. In short - a game world should ideally feel like it works independent of the player. While the realistic depiction of a game world is one side of the coin, a game can redeem itself with strong art direction and stylistic flair.
5/5 - A game has amazingly powerful visuals, with sublime animation to make the game environment appear as a believable, functional world. This can involve grass realistically being flattened with each step your character takes, trees swaying with the breeze or characters bodies recoiling realistically if under attack.
Alternatively the games art direction can be so well defined and appropriate as to successfully embody the game as a whole. This involves surface aesthetics, menus, HUD design or just the style of the visuals. A game can achieve top visual score with graphics which are heavily stylised and effective, but not necessarily powerful.
4/5 - Graphically strong, providing a good environment which feels believable to a point, though not entirely. Animation and character models do the job but are never cohesive enough to truly engage the player as part of the game world. If art direction is integral, then it is strong and helps to add to the feel of the game. The player interface is intuitive and the HUD is effective whilst not distracting.
3/5 - A game has graphics which are average for the time it was made. These visuals aren?t bad, but are unworthy of comment past their unwavering mediocrity. Graphics for a 3/5 game are functional in portraying a game environment, but never manage to lift itself out of the uncanny valley. Animation is stiff and you?re forever reminded that the characters and environments are but a series of binary numbers being endlessly crunched by a processor, rather than a real, believable world. Art direction is either non-existent or bland.
2/5 - The graphical poignancy is somewhere around that of a last-generation game. Frame rates are often slow, animation is wooden and character models are poorly designed. There is no chance of becoming immersed in this game. Menu design is unintuitive and the HUD is cluttered. There?s no artistic flair to speak of, and if a specific art direction was attempted then it was a failure.
1/5 - Your character glides stiffly across - and often through - a blocky landscape of cardboard cut-outs. Animation is like that of a power-point presentation and the art direction consists of ?let?s use yellow and green together!? Menu navigation is like using a spreadsheet.
Sound
The sound within a game consists of music and sound effects - not simply how good each piece is on its own, but how well they?re used within the context of a game. You don?t want a Wagnerian symphony playing during an intense sci-fi space-race for instance. The best games will use sound to reinforce emotions such as fright, elation, isolation or kick-assery (the feeling of being kick-ass, naturally). This includes sound effects as well, which can work to direct the players feelings as needed. If voice-acting is used in the game, then the lines need to be delivered with the appropriate emotion and need to sound sincere.
5/5 - A game expertly weaves the audio plain with the gameplay, visuals and the narrative, so that quality music or sound effects are played contextually. This can be to help direct players using audio cues, or to capitalise on emotional parts of the narrative. The audio expertly anticipate and then exacerbate the emotions of the player. The game also understands the importance of silence, using either sparse or no music to effect within the game when appropriate. Audio quality, including the quality of sound effects (the firing of a gun, the roar of an engine, etc) are of immaculate clarity. It should be mentioned that either an excellent original sound track, or a well chosen licensed soundtrack can be used in a 5/5 game.
4/5 - A game uses audio to effect in the game, playing the right audio at the right time for most parts of the game, but can also make mistakes in the use of sound to detrimental effect (using tense music as a signifier of danger in a game, before the player is aware of said danger for example). The sound effects are of good quality and voice acting, if used, sounds convincing. This is the type of game which gives a good auditory experience, but not one which you?d feel particularly compelled to put on your iPod.
3/5 - A game has an average original sound track that is used sometimes to good effect, but equally often used pointlessly. If a licensed soundtrack is used then it is poorly applied. A 3/5 game will consist of mostly ?background music? which is used simply to ensure the player has something to listen to, but doesn?t engage with the rest of the games elements to effect the experience. Sound effects are appropriate, but nothing special.
2/5 - A game worth 2/5 for sound will have a soundtrack that fails to achieve the desired result or just has music which is straight-up bad and unsuited to the game. Sound effects are of poor quality and voice acting is painful to listen to.
1/5 - It?s like you?re playing a current-generation game with an 8-bit soundtrack dubbed over. Either a completely incoherent soundtrack, or a complete lack of one, when music is actually needed. Sound effects are from several generations ago. Voice acting is either delivered by a zombie or in another language.
Gameplay
It?s difficult to discuss what exactly makes good gameplay. Different genres obviously have different criteria for what makes them great, so we?ll keep it to broad generalisations here. Gameplay is what separates video games from films - it is the capacity for the player to control and manipulate the game world. The most important thing is for the game to be intuitive. This will take into account such things as ability progression within characters, the difficulty curve, controls and amount of content available.
5/5 - The game controls as intuitively as possible, meaning that every mistake your character suffers is as a result of your own error - not the games. It never feels frustrating or unfair and continues to give challenge while not overwhelming. The difficulty curve and development of character ability is matched perfectly, ensuring a steady climb of challenge to a satisfying conclusion. If character customisation is in the game then all options are matched , balanced and kept well in check throughout the game. There are a wealth of options and content to keep a player engaged, meaning the game has good value for money. Controls are sharp, ensuring that every movement you decide to take it easy to convey to your character and level design is immaculate.
4/5 - The game controls well enough for you to enjoy the experience, and there are few control issues. A mostly consistent difficulty curve, with characters abilities balanced with the enemies well, although there can be instances of either disproportionate ease or difficulty due to bad pacing of the gameplay. Level design is mostly coherent and only sometimes confusing. Some aspects of character customisation can feel weak.
3/5 - The game controls are standard and for the most part allow you to enjoy the game, however there are instances of annoying control mechanics that don?t work as well as they should. Level design is bland, uninspired and forgettable. Character customisation is shallow and the difficulty curve veers off at certain points in the game.
2/5 - There are many crucial control flaws which make enjoying the game all but impossible and more than often or not failure is as a result of poor design rather than player error. There is little to no depth, option or variety available to you during play. Level design is a series of linear encounters that are as boring as they predictable.
1/5 - The controls are as broken as the game disc will be after half an hour of attempted play. The game is as balanced as a drunken, one-legged mental patient on a tight-rope. The levels and encounters are as boring, repetitive and tortured as my continued use of metaphors in this paragraph.
Narrative
Not every game needs a narrative - what sort of diseased, drug-induced story could you possibly tie to Pac-man for instance? Yet if a game is going to have a story, it had better be a good one. Narrative consists of the quality of the plot, the depth of the characters and the way in which the story is entwined with the gameplay. It isn?t enough to have a strong story told entirely through cut-scenes, as it becomes nothing but a film with intermittent gameplay segments. The best games narratives are inseparable from the gameplay.
5/5 - An enthralling plot with unique and empathetic characters with the nuances of the narrative linked inexorably with the actual play of the game. A 5/5 game needs all of this to be a game narrative worth remembering - and it?s worth remembering that what makes a good game narrative isn?t necessarily what makes a good narrative across other mediums. Character progression is strong and the plot is engaging, surprising and touching. The narrative of the game is informed and researched - it has weight behind it.
4/5 - This game has an interesting plot with strong characters but isn?t necessarily entwined as closely with the gameplay as it should. The story may be predictable or somewhat uninspired, but is written well enough for its shortcomings to be ignored.
3/5 - A decent, but predictable plot may not quite make sense. Characters are typically uninspired archetypes that fail to evolve a satisfactory amount throughout the games narrative. The story doesn?t have anything deeper to it than a series of co-inciding events, and it barely constitutes as a complete narrative.
2/5 - Annoying characters with no character progressions. A meandering plot with no substantial narrative behind it. This is the type of narrative where you?ll be mashing the A button to skip each tortured, irrelevant cut-scene.
1/5 - You fall through a giant plot-hole into the game world where you are introduced to the cast. You then feel compelled to find the nearest body of water to drown your character and the supporting cast as a service to society. However due to a series of baffling plot points which are never explained, water is nowhere to be found.
Multiplayer
The trend lately is for every game to include some sort of multiplayer feature, which to me seems wrong. Multiplayer is not something that can be successfully applied to every game. In a time when most multiplayer portions of a game require alot of invested time to fully appreciate, it?s becoming more and more important for a games multiplayer to stand out significantly enough to persuade players to pick that game to progress in. Due to the competitive nature of multiplayer, it?s absolutely imperative for a games multiplayer to have sublime gameplay. Nobody wants to play competitive multiplayer where the controls are an uphill struggle, or where the play is just plain unfun.
Added on to that, good multiplayer should also include a good degree of customisation, a positive approach to community and enough potential variety to keep playing the game exciting and fresh. Balance is also key, with things like weapons being required to all have their appropriate strengths and weaknesses to stop abuse spreading like wildfire throughout the community. Level design needs to be fair, interesting and unique to keep matches forever fun to play.
5/5 - Basic control of the game is immaculate, so that matches are purely about who is best at the game. Level design and weapon balance are both great, ensuring that games are all about skill rather than luck. There?s a wealth of customisation available to keep the player concerned with progression through the multiplayer ranks. There exists a wealth of options around the core multiplayer, and the game is supported by a developer with a caring attitude towards the games community, meaning the game is constantly changing and adding new challenges.
4/5 - The multiplayer is build solidly from a gameplay perspective, making it fun and fair to play. Level design and weapon balance is mostly fine with only a few isolated instances of unfairness. Additional options are there but mostly shallow or irrelevant.
3/5 - The game is built on mediocre controls, which translates to a mediocre multiplayer experience. There are inconsistencies in the weapon balance, and environments which may have worked well in the single player provide a poorer experience in competitive multiplayer. Customisation is either absent or shallow. There are much better multiplayer experiences available.
2/5 - A baffling multiplayer offering, built on already questionable gameplay. Matches are stagnant, uninteresting, unfair and frustrating. Level design is completely unsuited to competitive multiplayer.
1/5 - You can?t tell what the multiplayer is like because everyone else has already deserted this ship-wreck. If you?re (un)lucky enough to find a match, it will be with an obsessive max-level player who instant-kills you with the games equivalent to the BFG9000 while you attempt in vain to score a kill with a slingshot - the only weapon at your disposal.