Why do you want the ps3 version anyway? If only for supreme graphics pc game will always stay on the edge.

Can I use "stay on the edge" this way? What I try to say here is PC games will always have the cutting-edge graphics. When thought about this it just came right off my head, I don't know why maybe I've heard someone use it this way before.

Besides, what meaning do you usually use this phrase for? (If this is a phrase, I can't find it in a dictionary. and feel free to check my grammar )

No, you cannot not use “stay on the edge” this way if you want to refer to “being on the cutting edge” of graphics.

“On the edge” is an idiomatic expression that means “in a precarious position, or in a state of keen excitement”.

on the edge

1. In a precarious position.

2. In a state of keen excitement, as from danger or risk: "the excitement of combat, of living on the edge" (Nelson DeMille).

Excerpted from The American Heritage® Dictionary of the English Language, Third Edition © 1996 by Houghton Mifflin Company.
Stay on the edge = to stay ahead of the game, to be at the cutting edge of a field in business, to be ahead of the game.