PS3 and XBox 360 seem to be where emulator devs start running into issues, though a lot of the games for those systems aren't exclusives. Emulators exist, but it's not to the point where you can just fire up a random game and expect it to work out of the box.
If you haven't yet check out Syphon Filter for PS1. It's like metal gear solid but only the shooting parts.
PS2 is the big one. You've got that taken care of. Nintendo Wii with a softmod. I think PSPs are still popular for their moddability too?
PS3 and XBox 360 seem to be where emulator devs start running into issues, though a lot of the games for those systems aren't exclusives. Emulators exist, but it's not to the point where you can just fire up a random game and expect it to work out of the box.