Console or PC? Reason I ask is because ME2 plays more like a console game so it's hard to find a similar game on the PC.
Probably the closest thing you could find on the PC is Alpha Protocol which isn't bad, some people hate it, I thought it was alright.
*edit* Might also recommend, Fallout 3 & New Vegas along with Just Cause 2 though they don't play exactly like ME2, however the're great games with shooter/rpg elements.
*editx2* Also keep an eye out for Deus Ex: Human Revolution suppose to be coming out in 2011, I'm looking forward to it however I hope square-enix doesn't f it up.
All the Bioware games are pretty similar. I personally didn't like Dragon Age that much, but you could dip into Knights of the Old Republic if you haven't played it yet. If you're okay with older games I would look at Deus Ex, Elder Scrolls IV, and Vampire: The Masquerade, or Planetscape: Torment. If you want new games The Witcher and Two Worlds II are probably worth checking out, but let's face it, they're no Mass Effect.
