I think that HERO is arguably the most complete rules set ever written. And it is highly playable, too. A marvelous system.
It still kinda blows my mind how versatile that rules set is. And I never thought it was hard to pick up to begin with, after the basic concepts were in your head, because it was so consistent. After playing with it for years, I could still think of weird, random powers and abilities far beyond those of mortal men which I could easily (most often) sum up with a power and modifier combo. The main rules only took X pages, but conceptually, that system is bottomless.
On the downside, I had many (friendly) arguments with folks over Telekenesis. I think they changed it in 5 Ed, but in 4 it was NOT a way to move anything. It was STR at range and that was it. But folks got hung up on the name, "you move stuff around the room with TK, Jean Grey has TK, I saw Escape to Witch Mountain, I know TK when I see it" etc. Moving things was Flight, Usable on Others.
Hey, Myth, wasn't there a Variable Special Effects advantage? That can cover a lot of ground, i.e. you've got an Energy Blast, but it could be ice, fire, cosmic rays, magical ectoplasm, etc. changing turn by turn or encounter by enconter, as needed.
As for genre, well we played Champions, and I've only ever dabbled in any varient of Fantasy Hero. Our Super Heroes were generally straight up 80's style heroes. Dark Champions came out as things were waining, and I can't recall if anyone even picked it up. We had a broad variety of adventures, from preventing demonic incursions into the mortal realm, to preventing world conquest by mad men, to bank roberies. Used some 'core' villains and we created our own. It was a cooperative campaign, had about five players and everyone GM'd at least a bit if not a lot.
The best published adventure I ever ran in it was Wings of the Valkyrie, which started with a murder mystery and lead the heroes into time travelling back to the dawn of the Nazis. A great, well-written, well-conceived adventure with broad scope, wonderful dilemmas, and fun set pieces. I've been half-wondering about running it again at the con next year.
Totally random, funny Ace moment: Ace was vulnerable to teleportation. His powers were based on the vague concept of "bio-energy" (as if he had 1000 times of something that normal folks have but can't apply like he could) and teleportation disrupted the flow and caused pain. His best buddy was Rook, who's entire power suite was based on teleportaion effects. The two were having a tough time taking out a few bad guys, but finally the dice were rolling in our favor and the end was near. Rook asks Ace if he needs any help, and Ace confidently says no. Rook uses an area effect blast to take care of the two goons bothering him, while Ace is one segment away from clobbering his foe. But the edge of Rook's explosion just tags Ace's postiion. The damage from the blast is, like, 2 points, no problem. But it triggers the vulnerability! ...2d6 of damage later Ace is out cold, and Rook has another bad guy to mop up....