If I were going to do a systemless random supers generator, which I'm not, I'd have them roll for a theme first. The themes would be broad; so would skills be, because it's a trope of the system that "Dr." in front of your name lets you do any science-y thing. I don't know if theme would affect the roll for origin, but it probably determines which disadvantage/quality/aspect chart you pick from/roll on.
I'd use levels something like FUDGE or FATE: everybody starts at average and we're checking the deviation.
Then attributes overall, and give them points depending on how they deviated from "Excellent" because superheroes are gorgeous and wonderful-looking by default. They get to spend the points.
Powers...the biggest default might be a pyramid of powers, maybe like the FATE skill pyramid. (Other choices would be "One-trick pony" and "Broad and shallow"). That gives you a number of powers, so you then roll to see what they are and interpret them according to the theme you already rolled. You get to chose which one is great, which is good, and so on.