Is it that good? No, it is not.
Usually a highly acclaimed game is actually very good overall. It doesn't mean it's flawless, and it definitely does not mean that it will not ruin your experience with it because you happen to notice its flaws more often than not.
I'll give you some examples:
Portal: a short one-trick pony. I enjoyed it greatly but it lasted for 2.5 hours. Then I played it again for four more times, but replay value diminished fast- the only thing that remains now is map packs, that is more puzzles- in other words, more of the same. Still is a one-trick pony.
Baldur's Gate 1&2: great story arch and character interaction. Shaky gameplay, at times. I personally happen to love real-time turn based combat and have really gotten into the rhythm of pausing, issuing orders, unpausing, and repeating. So, that game kicks ass for me. I still hated the horrible pathfinding, the shameful glitches, and the crappy attack sprites. Also, if a character changed their body orientation, they became mirror images of themselves. That is, their left side became their right side, and vice versa. This happened constantly and got on my nerves after a while.
Rome: Total War: I can write a doctorate dissertation on how stupid the AI was in this game. Declining factions would elect to go to war. Full-stack armies would sit in a forest for ten years. Trade agreements would be neglected even though both nations would benefit. Successful factions sometimes let you conquer half of their territories before responding properly. That's one half of the game. The other half involved grouping bugs, where units wouldn't follow orders issued to groups to which they belonged. Besieging armies would stay put and do nothing if their siege equipment gets destroyed (instead of retreating and saving the lives of many soldiers, which were otherwise wasted walking back and forth along walls which _shot arrows at them_); besieged forces would sit on their walls and in the town, waiting for you to trap them and advance properly on them, provided your soldiers marched down a fucking street in correct fashion and didn't dissolve into a disorganized mob.
Call of Duty 4: respawning enemies has always been and will always be a terrible gameplay mechanic. Checkpoints sometimes never clicked on veteran difficulty, which made some levels nearly unplayable.
Bioshock: gameplay was too easy and provided little challenge to the player. Dying was more an inconvenience than a setback.
Diablo 1&2: pure hack-and-slash and no actual role-playing is involved in the game. The quests are very few in number and amount to little more than gameplay devices. The in-game story advances in a very methodical and cheesy way.
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So, no game is flawless. You can never know until you play the game. The reason we have reviewing standards and acclaim is because, like with all things, quality is a standard that most people seem to agree on. It is relative by definition. It is the sum of all opinions. It doesn't mean you will love the game, and it doesn't mean any game is assured to be good.
You must first know what you want and what you like in a game, and then find your niche. After that, look at the games that are well-known to do what you want a game to do. Bottom line is 'good' is too complex to simply attribute to reviews and mass-praise.
Any time you hear nothing but praise for a game, ignore it unless there's some objective criticism for it within said praise. Usually just praise means that the person has been satisfied and has either ignored or overlooked the flaws inherent in the game they were praising. Every game has flaws, and most of great games even have huge ones- it's just that their target market was given what it wanted more often than not.
Hell, MGS4 got a 10 on GameSpot. It's perfect for people who love the Metal Gear bullshit, but to me it's tiresome and nonsensical. I wouldn't have enjoyed that 10/10-rated game one bit, and I didn't. My friend, however, bought a PS3 for the bloody thing, and enjoyed the game thoroughly, from start to finish. See the contrast?
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