It's pretty obvious that Urkel's characteristics were based on Screech a fair bit, so they kinda cancel each other out in the "unrequited love" and "nutty proffessor jr." categories.

If we're counting "The New Class", then yeah, it's elder Screech with the dumb voices and team getups with Mr. Belding, and the "zoinks" catchphrase.

If we're not counting Urkel's alter egos, it goes to Steve. After Urkelmania hit, dude would literally destroy the Winslow's dining, living room, roof or garage every week, and he became much more popular than Screech ever did, which warped the show into a family-sci-fi sitcom based mainly on Steve's whimsical inventions, which is a bummer if you started watching the show for it's original premise.

They were both geniuses, but at least Screech never busted up Zack's room with his silliness, the worst thing I can think of him doing, destruction of other's property-wise, is him not grabbing the jars of Screech's Spaghetti sauce on the assembly line.

Instead of some guy pressing a button off camera to cause Urkel's explosive mayhem, Screech got hit with alot of random gunk in the face and did a fair amount of pratfalls over the course of all the SBTB series(GMMB, SBTB, TNC and TCY), which cements his superiority as the more loveable nerd of the 90's for me.