in addition to the posts above:
Not all PS3-systems are backwards compatible with PS2 games.

I have an 80 Gigabyte verion which is not capable of doing so,

A friend of mine has the 60 Gigabyte version which IS capable.

I bought the PS3 instead of the XBOX because the "You-just-got-screwed" factor from microsoft is too high. Pay for online play, pay for DVD-kit, worse quality discdrives, etc.