20GB: 95% PS2 Games
60GB: 95% PS2 Games
80GB: 80% PS2 Games
40GB: Does not play PS2 Games, but plays PS1 Games
The 20GB and 60GB has the PS2 Emotion Engine.
The 80GB has the PS2 Graphics Chip, no PS2 Emotion Engine which results in emulation.
The 40GB does not include the PS2 Graphics Chip or PS2 Emotion Engine.
I haven't ran into any problems with my 80GB PS3. Only game that gave me problems was Ratchet and Clank: Going Commando. On Sony's site it says that the game slows down on the PS3. Basically the framerate drops when playing that game.
Other games work, like the MGS: Essistenial Collection and Devil May Cry series.
If you have any games you want to play on your PS3 that are PS2 games I suggest you use this feature that Sony put on its site :http://www.us.playstation.com/Support/CompatibleStatus
That link gives you the option to see if the PS2 game is backwards compatiable with the game you selected. If its not shown up then its not. If it is then it might show the problems assicoiated with the game or it might be without problems.
