Of my 360 collection my top 10 in order would be:
Bayonetta - What can I say? This game just absolutely blew me the fuck away. Everything about this game was incredible and it's actually my favorite 360 game and I don't even like these types of games.
Left 4 Dead 1/2 - I love killing me some zombies and you get to kill a lot of zombies in this game. As an added bonus the controls are wonderful on the console and work *really* well for me. I generally don't like multiplayer only games like this, but I gladly play with complete random strangers to kill some zombies.
It's odd that my top two games are games I don't generally like...
Dead Rising - Again, I love killing me some zombies. I would like this game more but I've never gotten past the first damn day. I keep starting over because people keep dying and I'm a completist about some things. XD
Fable II - The game itself is kind of lackluster but the ending, man oh man, the ending rocked my socks off.
Bioshock - The gameplay got a little meh towards the end, the ending boss fight sucked, and it even had a horribly lame fetch quest before that but this was just a really good game. The twist at the end is totally worth everything and it's a thrill walking around the ruined Rapture.
Call of Duty 4: Modern Warfare - I avoided this game for the longest time because I'm not that hardcore of a shooter fan but I loved this game. Everthing about the gameplay was just masterfully crafted and nearly pitch perfect.
Gears of War 1/2 - I only got the first Gears because I had just gotten a 360 and didn't have much else to play. The first time I played I got annoyed with the controls and gave up. Much later I gave the game another go and I'm glad I did! Once I got a handle on the control damnit I loved this game and then the sequel came and just improved upon everything the first started. Yeah, the story sucks but the gameplay is top notch.
Mass Effect - So I still haven't finished the game but I know I like it. There are many many many many little gripes I have with it but it's just so epic and everything else is so good. I can't wait to dig into Mass Effect 2.
Ghostbusters: the Video Game - I know what you're thinking, I'm just throwing this on here so I can whore it out but I actually do like this game! Still! Ghostbusters is easily one of my favorite movies of all time and this is a Ghostbusters fan wet dream. Without a doubt the game has its fair share of flaws, but I can look past all that since it means I get to saddle up with Stantz, Egon, Winston, and Peter.
Borderlands - I haven't done a lot with this game and it's pretty rough around the edges but I still really like it. I played it by myself and it was meh but then a friend finally made me play co-op with him and it was a blast. I can't wait until the next time we're both actually free and can have another Borderlands session.