When the 3GS was released, it had better graphics hardware than the 3G and support for OpenGL 2.0 ES. The difference in game graphics between the 3G and 3GS was pretty huge...
Apart from the screen resolution, what are the graphics hardware and software upgrades in the 4, and what is the graphics level going to be like compared to the 3G and 3GS, and other handhelds like DSi, PSP etc. ?