Brainy isn't a robot; he's a Coluan:
http://en.wikipedia.org/wiki/Brainiac_5 (yes, I know, Wiki...but still a good source for bio info).
As for Majestic, even for a Kherubim, he's very smart, and not in the way Superman is smart. He can research and build tech Reed would love to get, rewrite Kryptonian programming in seconds etc.
Originally posted by Golgo13
I forgot the Chief from Doom Patrol. If you count him as a hero. He's smarter than Will Magnus, IMO. Probably on the level of a Hank Pym by feats.
There's something....familiar about him. Can't quite place it, almost...Professor-like.
Won't count him as a hero though; bit of a dick, really.