http://pcsx2.net/
Probably old news for some of you, but the PCSX2 PS2 emulator has matured to the point where it runs most of the popular games at a good framerate and very stably. Later Generation PS2 games do not run as well (Metal Gear Solid 3, etc.) because they strained even the PS2. But the popular stuff such as FFX, FFXII, Kingdom Hearts I/II, various Star Wars games and other PS2 classics run well. You can either rip your games to hard disk or run them off your DVD drive. MAC OSX version is in the works too, but still has issues with the OpenGL rendering.
Recommended minimum for the best experience at 60fps NTSC framerate.
Intel C2D @ 3.0GHz or C2Q @ 2.66GHz | AMD Athlon X2 @ 3.2GHz or Phenom X4 @ 2.5GHz
2GB RAM
nVidia 9800GT/ATI Radeon 4850
Emulator has high specifications because the PS2 runtime engine is hard to emulate because the architecture differs greatly from a standard computer. For those inclined they explain more in the dev sections of their site.
Even after all these years FFX still looks good at high resolutions.
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