I've had a great RoleMaster game with just the DM and I...but I know that RoleMaster is probably not a good suggestion without better knowing the participants.
In the superhero genre I've done 2-player games in Marvel (MSHRPG), Mutants and Masterminds and Champions.
I have heard (can not confirm) that Savage Worlds is okay, but that the Deadlands game from which it sprang was a little better for 2 players.
Hope that helps!
- M