Playing ps2 games on another system? let me enumerate.
PS3 = Not all models compatible, good emulator
PSP = Almost all games work as long as it's converted, there are forums with literally hundreds of ready to play ps1 games, the only problem with this is no buttons for the r2 and l2, good portable emulator
PC = ( > medium spec gaming rig ) plays EVERY game ever (ISO and CD, PAL and NTSC), superior graphics options (anti-alias, af, smoothen graphics) and easy to use (wizard installer), best emulator you just need to buy a gamepad for it which even the cheapest make can suffice.