Dammit, I had a fantastic post ready: ''You aren't logged it anymore'' *facepalm
Anyway… the PS2 has a lower resolution, fewer assets and fewer polys. A lot of games on PS2 indeed ran 60FPS. Take your pick. A game that looks beautifull or a game that runs better than good. Cause 30FPS is good.
There are many grogeous games on PS4. Alien: Isolation, Dragon Age: Inquisition, Shadows of Mordor. All of them 30 FPS. If you want 60 FPS you're looking at sports games and Minecraft, mostly.
…..
I can vouch for a swap between the same game. For example, I have played Mass Effect 3 (2012) on both PS3 and PC (ultra everything). Does it run better? No. I mean yes, it does. It has 60 FPS instead of 30 FPS. Do I feel the difference? No. Did I try to feel the difference? No, because way back when I didn't even know there was a difference!
60 FPS will become a standard, I'm sure. But right now we're in the early stages of next gen consoles. Eventually we will probably swap, but now isn't the time that is likely to happen.