Gurps: Supers also had a plethora of sequels. Gurps: ISTs (international super teams, kind of like un peacekeepers) gurps ists adventures, gurps supers adventures, gurps mixed doubles (which was just goofy), and of course Gurps Wildcards and it's supplement Aces Abroad. I can't say that I really cared for their supers system or the stain it left on countless later products. But I do like the Wildcards. I really wish they would make some more of those books. What ever happened to them?
Excel Marketing put out the now-defunct Heroes and Heroines game/line. It was an interesting experiment: Instead of one hero-world, one set of rules they had multiple worlds (Continuity, Image/Maxx, and Dark Horse Heroes), one set of rules. Down side of it though: Most people couldn't stand the rules (me, I found them to a 'dryer' form of Champions...not New Millenium version though; but the good-kind )
I've always found the basic system from New Mildew to be quite playable.
I use it for PBEM and ignore about half the combat and movement rules. Basically, just roll for initutive, roll to hit, roll for damage. Compare movement rate to see whom can catch who, hand wave the all important knockback and property damage with whatever seems cool.
Task resolution is mindlessly simple, the way I like it.
Of course, the darn C:NM Book has a lousy layout, no index, and even more typos than industry standard. The last MIGHT have been fixed in the second printing.