The thing with generic systems is that while you can generally plug in different trappings into the system, the game will still feel the same. You can play GURPS with swords & spells, or as a Western, or as a Victorian vampire hunter, or as a 40s noir detective, or set on a far-future spaceship. In either case, you're still dealing with a game with hundreds of skills, a strong emphasis on attributes (particularly Dexterity and Intelligence, as those are what most skills are based on and the huge number of skills means it's more efficient to pump base stats), low skill defaults unless your stat is super high, a combat system which slices things down to seconds and uses fairly detailed hit locations (with different effects) and different damage types. There are some things that can soften the game a little, but it'll still fundamentally be the same game.
You can also play either of those settings with Savage Worlds. Savage Worlds has 32 skills (with the potential to add more if needed, but the skills are pretty broad), and while core stats play a role in skill development it's not as big as in GURPS (primarily, GURPS stats set the skill floor from which you build up, while Savage Worlds stats set a soft ceiling above which it becomes harder to increase a skill). Characters are fairly broadly competent, at least PCs which get to roll a Wild Die meaning that even without actually having a skill they have about a 50% chance of success at a regular-difficulty task. Combat in Savage Worlds is pretty fast and not as lethal as GURPS, and hit locations only matter if you take serious injuries. Oh, and Savage Worlds have a metacurrency in the form of bennies, which lets players add extra oomph when it matters.
Or you could do either of those settings in FATE. In FATE, you have a smaller number of skills, and skills also take the place of things that in other games would be attributes (e.g. Strength) or social traits (e.g. Resources). Equipment matters little, and a large portion of the game mechanic revolve around gaining and spending FATE points, which makes your Aspects very important as those are the main vehicle through which you do this.
My point here is that a swords & spells game in GURPS will be more similar to a Western in GURPS than a swords & spells game in Savage Worlds or FATE. It's like the samurai movie Yojimbo: you can transplant it to a spaghetti western and get A Fistful of Dollars, or to the prohibition era and get Last Man Standing, but either way it's not going to be Shanghai Noon.
I haven't seen the last few versions of M&M, but my impression is that it takes a very simulationist view of supers, as channeled through the d20 system. Characters have distinct powers that can do distinct things, and while there's a fairly flexible system for Alternate Powers (using the same narrative ability for multiple mechanical powers, such as using "Webshooters" both for making binding attacks and for swinging movement) and the occasional improvisation, the focus of the game is on the mechanical aspects.
Thing is, the super-hero comics I like tend to be much more narratively focused. The podcast X-Plain the X-Men (which is well worth listening to) proclaims the X-Men to be "comic's greatest superhero soap opera". I mean, it's all well and good that Rogue can punch you from one state to the next, but the really important part is if she can forgive Gambit for his unwitting role in the Mutant Massacre. And I don't think M&M is the game for that. I'm not sure any game is, to be honest.