As a refrence:
20GB and 60GB (NTSC): fully backward compatable.
60GB (PAL) and 80GB (NTSC): Software Emulation.
40GB, 160GB: No backward compatability.
80GB (new, 2 USB ports): ???
The new 80GB isn't supposed to support PS2 games, but it does for me as well. Wikipedia also states the new 80GB shouldn't be able to...Either way, MGS2/3 are supported on all PS3's except the ones the explicitly don't allow PS2 games to run.