I applaud you sir on your differing taste in games!  While I know I don't like some games in your list it's nice to read some refreshingly different lists of other gamers.

No specific order

1- Halo 3
2- Mass Effect
3- Gears of War 2
4- Halo Wars
5- Assassin's Creed II
6- The Orange Box
7- Bioshock
8- Fable 2
9- GTA: EFLC
10- Crackdown

1.geometry wars 2
2.geometry wars retro evolved
3.braid
4.portal(orange box)
5.street fighter 4
6.mirror edge
7.n+
8.virtua fighter 5
9.left 4 dead
10.bioshock

This should be easy, since I only own 11 360 games, ( Excluding XBLA games) and I don't even have to think, to know which one doesn't make the cut. (SoulCalibur IV.)

10. Bayonetta

9.  Dead Rising

8. Just Cause 2

7. Assassin's Creed II

6. Mass Effect

5. Fallout 3

4. Grand Theft Auto IV

3. Red Dead Redemption

2. Mass Effect 2

1. Bioshock

EDIT: The original Assassin's Creed, Arkham Asylum & Bioshock 2 would've probably been on the list, if I hadn't played only the PS3 versions of those games.

In no order:

Bayonetta

Lost Odyssey

Resident Evil 5

Mass Effect

Mass Effect 2

Dragon Age

Fallout 3

Marvel vs Capcom2

Shadow Complex

That's all I can think of that I've played and feel feel that it deserves to be on a positive Top anything list.

Bearing in mind that I buy most games for PS3, this list is missing some of the top multiplatform {also, whilst I own Alan Wake, I haven't played it yet}

1. Halo Wars
2. Mass Effect 2
3. Gears of War 2
4. Shadow Complex
5. Lost Odyssey
6. Mass Effect
7. Secret of Monkey Island
8. GRiD
9. Assassin's Creed
10. DiRT

It is very very close between 6-10 and there are another 4-5 that could go there

I can only put 9 games because I dont wanna put multiplatforms.

1. Alan Wake
2. Fable II
3. Mass Effect 2 (Im guessing here, I haven't actually played it)
4. Mass Effect (same here)
5. Kameo
6. Halo 3
7. Forza Motorsport 2 (haven't played Forza 3 lol)
8. Dead Rising
9. Gears or War 2

1) Halo 3

2) Mass effect

3) Mass effect 2

4) Gears of war

5) dragon age origins

6) Lost odyssey

7) Fallout 3

8) Alan wake

9) Forza 2

10) Gears of war 2

Just a quick one, not in order.

Gears of War 2

Mass Effect 2

Super Street Fighter 4

Halo 3

Lost Odyssey

Bayonetta

Shadow Complex

Fable 2

Alan Wake

Braid/Limbo (couldn't decide)

Uhm. As you only putted two multiplatforms there one doesn't know how you thought. Why not go all out and put more multiplatforms you like, or do you mean that the X360 xclusive library is that strong?