Sees like were missing some.
I just covered the Demon Princes, not the Devils. The Devils seemed to have chanegd around so much I didnt bother going over them. That, and I am lazy. ;-)
But since its been requested:
Asmodeus: 3E. I like Fisch's pic here, its abstract and strange, but still menacing. Could be the pentragram staff or the skull that Mr. A is absentmindedly tossing. The 1E Asmodeus is not bad, but again, pretty literal. The blank eyes never worked for me.
Baalzebul: 1E by a longshot. The original fly-eyed guy with his stark lines and crossed arms; look at that body language. ;-) BoVD is damaged by the conception, is there anything you can do with a giant slug to make it look cool? Probably, but its not easy and the BoVD artist didnt find the answer.
Dispater: Tossup. The 1E is a crude little quirky guy with his bald head, cloven hooves and tail. He's not high art, but he's got personality. The BoVD guy is a much better rendering, but altogether lacking in personality. Seriously, cover his name up and ask someone to guess if its Dispater, Fzoul Chyrnobyl (what is that guys name!?) or "generic module villian".
Geryon: 1E, by default. Apparently Geryon got the shaft during some infernal dealings and is now biding his time in an iron box next to Asmodeus' infernal toilet. The old pic wasnt that great and would have been slaughtered if it had any competition. Like the new Mammon. That thing is great.
Well almost all points. Graz'zt did indeed exist back in 1e.
For me, 1E is only the core books, because thats all I bought back then. ;-) So if its not in the DMG, PHB or MM it doesnt exist for me. I realize that its self-centered, but thats the way it is. ;-)