I actually enjoyed the voice acting in Battlefield: Bad Company.
I may not have enjoyed that game overall, but I found the banter to be refreshing.
Bioshock, obviously. The recordings were really well done. And the accents weren't horrible.
I like the voice acting in Fallout Three as well. Sure, there were times when it wasn't so spectacular, but atleast it sounded like they tried and were interested. Aside from the occasional typo in the dialogue...
Worst: Oblivion. The dry, monotone, identical voices of all of the characters got on my nerves.