Sony only made one model that had PS2 backwards compatibility and none of their current models have it. That one model only had backwards compatibility because they put PS2 hardware in it alongside PS3 hardware. Too costly so they stopped making that model which means PS3 does not have backwards compatibility with PS2 games anywhere and not just OZ. Sony does sell some PS2 games at their online store that have been ported to PS3 though, a few PS1 games too.
I have PS3 now and had 360 before too. Form me PS3 is better only because of BluRay and better quality hardware, isn't noisy like my 360 was. 360 has a better game library though. Wii is not even a contender because it is mostly kiddy games that do not appeal to me.