almost all recent custom firwares can .. you can either just get the PSN versions of PS2 classics that are officially available (from sources like psnstuff, in those cases you just gotta install them and play) .. or download custom converted ps2-to-ps3 games on sites like ps3 iso, you'll need to install the 'ps2 image' mounting app on the ps3, it's really simple, you can find pretty detailed tutorials on ps3iso.com etc