Fable 2 was quite an experience, but I played at launch, and I was absolutely immersed into it. But it has really bad glitches, my daughter ran away to be an adventurer like me and I went to save her, and I did but when we came out of the cave she was stuck and would not move, I reloaded and same thing, over and over. There were tons of other glitches but that one bothered me the most.
Fallout 3 has just as many if not more glitches, but they didn't annoy me quite as much as Fable 2's. Both are great games, but have their share of glitches.
Oblivion was a great game, I never finished or beat it and never played through the bonus content so I think I'll personally be picking up the GOTY edition soon.
Only thing that kept me playing Mass Effect was the great voice acting and music, especially that little tune when you open the galaxy map. Other than that, the game feels really clunky and dull. I personally didn't like it much.
Kingdom Under Fire: Circle of Doom was a terrible game in my opinion, it hasn't been mentioned but if you come across it I recommened skipping.
I'm not much into JRPGs but I will get Lost Odyssey, Tales of Vesperia and maybe Star Ocean eventually to play through.
Still waiting patiently for Final Fantasy XIII... and am currently looking forward to
The Witcher: Rise of the White Wolf for Xbox 360 (which I thought was gonna be released in the next few months but after looking up a bit it's all saying 3rd or 4th Q). Also might wanna check out Rise of the Argonauts but I hear it's not really that good, I planned on getting it on its release date but bad reviews have kinda made me change my mind on it, but I still will check that one out eventually.
So (IMO), the good: Fable 2, Fallout 3, Oblivion. (in that order).
The bad: Mass effect
the ugly: KUF: CoD