I was watching one of the more recent animated Justice League movies tonight. Whenever I watched animated DC stuff, I always get the urge to play Champions 4th edition, even though I don't particularly like the system. Champions 4th was the first, and presently only, superhero games I've ever played....and boy, did we play the hell out of it in junior high and high school. I rarely ran the game, preferring mostly to play it, but I recall the system made me fairly miserable and character creation was mostly an arms race. Still, we did have fun with it for the most part....and the parts that weren't fun still make damn funny stories.
The truth is, I have never been satisfied with a superhero role-playing system, though I must admit I have had relatively limited experience with them. Besides Champions 4th and HERO 5th, I tried to design a supers game using FUDGE, though I never finished it. I own the revised version of Mutants & Masterminds, though I could never really get into it. I have the PDF of Necessarily Evil (a super setting for Savage Worlds) but I seem to put off reading PDFs for months or years at a time. Oh, I almost forgot... I have a boxed set of the DC Heroes game from WEG that I picked up at a 50% off sale two summers ago.
I have heard of a number of other superhero systems, but truth be told, I've sort of given up on looking for a decent system. I think that superhero gaming is one of those problematic genres that just don't "game well" (another genre I don't think games well is mecha, but that is another post for another day.)
I suppose one of the problems facing superhero games is the sheer disparity of power levels between heroes, often in the same universe: Jubilee can shoot pretty sparks that seem to be capable of little more than stunning foes, while Magneto seems to pretty much have any capability that can be loosely tied to the concepts of magnetism. The Green Arrow is a skilled archer and martial artist, but Superman can withstand tank shells and hang out in space without protective gear. Meanwhile, Aquaman talks to fish.
I think my desire to have a supers system I'm satisfied with stems from my need to have a "go-to" rpg for every genre. Once again, I recall the maxim that there is a fine line between hobby and mental illness.