1. Halo 3 (great campaign, multiplayer, and forge)
2. Halo: CE / CEA (astounding campaign. Two Betrayals is the best Halo mission in history)
+custom edition - I love all the custom maps! Even made walkthroughs on a few
3. Modern Warfare 2 (extremely fun multiplayer, fun Spec Ops, and a good campaign)
4. Gears of War 3 (HORDE HORDE HORDE HORDE)
5. Minecraft (It's plain out amazing. 'Nuff said.)
6. Borderlands (Other than the weak ending it was very good)
7. Halo: Reach (Amazing forge and a good multiplayer)
8. Just Cause 2 (Unlike GTA, you reap havoc and chaos for a GOOD purpose [bonus for massive game world])
9. Trials: Evolution (This game is simply amazing and has the best world editor possible)
10. Metal Arms: Glitch in the System (This old game was loads of fun, but had a lack of online multiplayer)
Honorable Mentions (these are in no specific order)
-Crysis 2 (Very addictive campaign)
-Forza Motorsport 4 (A well mastered racing game)
-Team Fortress 2 (Like the variety throughout w/ servers, characters, and items)
-Tribes: Ascend (A lot like a mix between Halo and Team Fortress 2 + supersonic speeds)
-Left 4 Dead (Much better than the 2nd, it is very fun and masters campaign maps)
-Halo Wars (Halo wasn't meant to be a RTS, but it does it pretty well)
-Star Wars Battlefront II (Good campaign and multiplayer [love hunt and jedis])
-TES 4 and 5 [Oblivion & Skyrim] (Adventuring all around is very fun, and questing is great)
-Pokemon Mystery Dungeon Blue (I just love the way it works)
-Pokemon: Pearl (This is personally my favorite Pokemon game out there, not counting Mystery Dungeon)
-Super Scribblenauts (The idea was already amazing and adjectives made it better)
-Mechassault (Another oldie, love stomping around in huge mechs and destroying stuff)