I like a game with moderately strong tutorials and item descriptions in place.
I'm playing Elder Scrolls IV: Oblivion for the first time, and I have to admit, I'm not terribly pleased with just how much it DOESN'T tell me. You pick up soul gems! Cool! What the hell is a soul gem? What's this weird crystal thing I just picked up? Gosh, it'd be really neat if the game would give me a two sentence description. How I do alchemy? Trial and error? Well... that sorta works, I guess, but I get the feeling I'm wasting these rarely-seen herbs and seeds.
I like some cover-based shooting combat. I'm playing Half-Life 2 and I'm crouched behind a wrecked car. Does that make me safe from the sniper in the window up there? I won't know until his sight is on me. Meanwhile, in Mass Effect 2, I'm crouched behind some stuff and I KNOW I'm safe from anything thrown my way.
Read: SOME cover-based shooting. Mass Effect 2 hit a happy medium, I think, between old-school "hide around a corner, strafe out to take pot-shots" cover and Gears of War "glue yourself to the nearest chest-high wall" cover.
I like a game that plays with what constitutes difficulty. In Halo, on easy mode, you can scare away the grunts, especially after shooting their leader. On Legendary, everything and their pet is ready to take you on with a bravery only matched by their unerring aim.
I like a game that changes up the music depending on the mood. LoZ: Twilight Princess plays this very well by making the boss music suddenly switch to "now is the moment of glory" mode every time the boss becomes vulnerable. Some years prior, LoZ: Majora's Mask had a different variation on the main Clock Town theme for each day.
I like a game that has some kind of larger-than-life boss battle. One or two is plenty for me, although I like more as the game permits.
I'm a little disappointed in Mass Effect 2 for not taking advantage of the fact that we're in a future where damn near ANYTHING is possible through the use of mechanical technology and biotics, yet 95% of all enemies are the same size as you, and the big tank-type mechs only barely makes the 5% because there's a handful of them in the whole game.
On the complete opposite end of the spectrum, Shadow of the Colossus. 'Nuff said.
Speaking of boss battles, I like games that don't have giant fuck-me light weak spots. Legend of Zelda is a pretty big offender here, along with Shadow of the Colossus.
On the other end of the spectrum, you have bosses that you can hit just anywhere and it all does the same amount of damage. I'm playing World of Warcraft, fighting a boss three times my size. How, I ask you, is this thing getting horribly owned by us blasting the crap out of its feet/legs?
I like games that tend toward the fantastic. Want me to play an FPS? God help you if it's Call of Duty, because I don't want none of that. Wait, Half-Life? GIMME! Bioshock is great partly because it's a 1950's dystopian sci-fi comic made into an FPS. Bioshock Infinite is turning up the fantasy to 11, and I have zero complaints about it.
And yet, it can easily go overboard, especially when we're talking about sword&sorcery games. I think one reason why Elder Scrolls works so well is because it never allows itself to get all whimsical. Yes, magic saturates the world, but you never see the Harry Potter levels of magical whimsy, do you?
