Uncharted 2 has nothing on Mass Effect 2 in terms of acting. Even the first ME blew it out of the water.
BioWare are the masters when it comes to the atmosphere and stuff like that.
Uncharted 2 was a really good game. But it is very linear. It is telling you a story and it can be done in only one way. ME2 is telling a story but giving you various paths to do it in and various places to choose from. They are two totally different games in that regard.
Uncharted 2 = good. Mass Effect 2 = great in my opinion.