I feel like ZSS's up tilt is only seen as good because her up air is ridiculous.
That has nothing to do with it XD
It's frame 3 (making it a great OoS option), has huge
horizontal and
vertical range, does 12% and true combos out of dash attack after ~30% on the entire cast, except for Kirby.
You can also frame trap with it on your opponent's landing, if you fall with them (below them) and do something like uair/back hit nair (they airdodge this) --> you land --> you utilt them.
It has its risks, ie being unsafe on hit at very low %s (like 5% and below) and very unsafe on shield/whiff, but when used properly it's great.
As for my top 5 utilt list,
Snake, Fox, Pikachu, ZSS .... there are a few others with some really good ones that all kinda do the same thing (Diddy, Lucario, Kirby, Mario, Luigi, Puff all combo well at low %s...though Diddy's also kills) and then there's also DK's (good landing mixup, quick and good damage), DDD's is pretty good...Bowser's and Squirtle's are also good...I'll say 5th is Diddy's
@Delta, I'm assuming the latter.