Considering the ease of emulation, how one can use it as a home console, and the surprising library of games...yeah, PSP ranks high on the list.
Anyone looking for something unique to play on it (or Vita), try Half Minute Hero. (There is a PC version, but PSP version is better IMO.) There was also a tac-RPG by the makers of Disgaea about a superhero, starts with a Z...Zettai maybe? Great game, anyways.







