16-bit is about as good as you need for most 2D games. More powerful systems give you better 3D of course. I guess you get higher resolution and more colors for 2D games too but that doesn't always make them look better. You also get more things on screen at once if you are a fan of "bullet hell" type shooters with millions of things on the screen at once. But to me the best 2D shooters and platform games are still 16-bit.