Roronaa_chan on 11 July 2015
They really should prioritize PS2 emulation
PS3 is recent, and also available on psnow (which means available on PS3, PS4, Vita, PSTV/TVs/other devices)
PS1 games run on PS1, all PS3s, and (select psn store titles) on Vita
That leaves PS2 games running on nothing other than PS2 and the first PS3s (many of which already died, including the one I had). I know there's a few ps2 classics on PSN that run on any PS3 but it's an even smaller number than PS1 titles (at least in EU). It's also a lot less demanding, the PS4 is capable of it, and probably with some improvements (resolution/framerate).
