I already gave my views on 3e art vs. prior edition art (covers and full-page color pieces: 2e; overall interiors: 3e) in the Iconics thread, but one thing did leap out at me in this one.
The design, as opposed to the art, of most of the 3e and also 3rd-party d20 books is gorgeous - far, far surpassing that of prior editions.
I flip through some of the newer material, especially the Eberron and Dragonlance campaign books, and oh it's easy on the eyes. Compare that to TSR's pairing of black and blue. Except for the gorgeous full-page art, 2e books looked like a bruise!
But this is really about WotC-only art, so leave Dragonlance and Sovereign Press out of it.