1. Bioshock
2. Mass Effect
3. Crackdown

The # 3 spot was difficult... it was either Halo 3 or Crackdown.... Even though I have played Halo 3 sooooo much more, Crackdown was just a different experience.

1- Halo 3
2- Gears Of War
3- Bioshock

1. Gears
2. Forza 2
3. Bioshock, no wait, Crackdown. No, Bioshock, Crackdown. I can't decide. :(

I don't own one[360], but I've played them.

1)Gears of War
2)Ninja Gaiden 2
3)Mass Effect(only 360 game I've finished)

From best to not better than the best (lulz):

3. Halo 3;
2. Bionic Commando Rearmed;
1. Mass Effect.

1. Gears of War
2. Earth Defense Force 2017
3. Stangle Hold
... actually scratch that

my favorite 3 360 games are
1 Earth Defense Force 2017
2 Gears of War
3 Bionic COmmando Rearmed

Frankly I think EDF is the most underrated game this gen, this isn't a jab at the 360's library at all, edf is a genuinely fantastic game, I know some people speak positively of it as mindless fun but on the harder difficulties it transcends from mindless blasting to really careful planning and strategic thinking, try spearhead or eruption without carefully planning on anything past normal and just reacting and shooting won't win
plus the story line is actually really entertaining if you listen to all of the background chatter, and frankly starship is probably one of the best last stands ever in a video game
plus the genocide gun makes the bfg 9000 look like a peashooter

1: phantasy star universe (750hours+ )
2: pgr3
3: enchanted arms

1 Mass effect
2 Bioshock
3 Gears Of War

1 Bioshock
2 Mass effect
3 Gears of war

1. Tales of Vesperia
2. Geometry Wars
3. Banjo Kazooie arcade (I don't care if its not out, its a port of a game I have already played and loved, with new content)

3. Oblivion (in case BK doesn't take)