my favourites are: Bad Company (hillariously awesome) Munch's Odyssey and Halo 2
Halo 2 and 3 both left room for a sequel and did an amazing job for opening a gap
honourable mentions: (those that didnt make the top 3)
Franks Adventure (all of them)
N3 (only the Girl with the watermelon landslide and near enough no armor and the hench blokes one)
CoD4 (left us thinking, and was a great way to end the game, nothing like a little bit of realism, not everybody survives war and that war is unlogical, anything can happen; you just have to think to see this)
Crackdown (I actually saw this one coming as i climbed up to the ENIGMATC WANG!)
Lego Star Wars (there was no ending XD)
Fable:TLC (yet to finish 2, heard bad things about the end though)
Ratchet and Clank TOD (great suspense, cant get quest for booty however
)
R&C 2 or 3 (the one where you get dropped onto the robot world in the war against Tyrranoid's and Britney Spears is cameod by a robot)
C&C 3 [NOD] (The GDI ending was a little pussyish until Lando Calrissian came on screen - GO LANDO!)
and now my least favourites: NONE! love em all really