West End Games' DC Superheros is a good place to start, but then, I'm a fan of most of what WEG used to do. You can get the pdf fairly cheaply, or pick up the core book.

Then you have mutants and masterminds, the grandaddy of superhero systems, which works really well, and scales a bit better than DC Superheroes, and the third edition pdf is available fairly easily, and they produces a DC Superheros skin for the game, and that's even easier to find. This system works really well for both dark and light superheroe games.

Then there's Brave New World, and iconic superhero RPG. Difficult to find these days, but the setting is fun with a leaning towards a Watchmen feel.

If you're looking for less super, more hero, then something like The Laundry is fun, and a very fun upbeat setting. Then you've got 'Is It A Plane's, an unusual system,, but really story driven and leans into the comic-book approach.

An honourable mention to GURPS, because you can play pretty much anything in it, including superheroes and you can get that dirt cheap on the internet.

Hope that helps!

I really like the sentinels comics rpg - https://www.greaterthangames.com/pages/sentinel-comics

It's based on the sentinels of the multiverse card game, and has a really unique system. Basic low down - every roll you have die based on a "stat", a power, and your (or the scene's) status (green, yellow, red).

On a basic roll, you always take the middle die as your results. Powers might alter this or do something extra.

So for example, let's say you have super strength as a stat for a d8, a power die of a d6 for the power you're using, and a d6 for your current status (green). You'd roll all three of these and take whatever value is the "middle" result (so like d8 - 2, d6 - 4, d6- 5, you'd get a 4).

Powers might do something like "deal damage equal to the lowest die, but heal an ally for the middle die" or "deal damage with the highest die, but take a penalty equal to the lowest die"

Champions

https://www.herogames.com/hero_system_basics.html/

I used to play some previous editions. It's extremely flexible. It's a point buy system. It has, for example, ways of defining a power that requires something external (which makes it cheaper in points), e.g. flight using a jet pack, and if that thing can be taken away. So you could build a Spider-Man that has web shooters that require ammo or you can make the one that spurts ropes right from his wrists.

It's also flexible in that there are two types of damage. The first is more for a more brawly combat where you get them down to 0 stamina (or whatever it's called) and they're unconscious. Then there's killing attacks that go for hp with an eye for making the other character dead. This makes it very easy for codes of conduct (e.g. no killing, which is also done with points) to easily be defined mechanically. Attacks can also be defined by what they can get through, like a psychic attack won't be dampened by physical defense (but might have a weakness against unobtainium).

There's also ways to build plot into characters. You can buy things like people important to your character ( that you may have to rescue), sidekicks, information contacts, nemesis, superior officers, organizations, etc.

My group managed to make great knock offs of Superman, the Flash, Iron Man, etc., but also had no problem with making a Sentai squad or a character that could copy abilities by absorbing them (which I suppose both MegaMan and Rogue do, but in different ways which you could define with this system).

And depending upon how many points you play with can determine if you're doing Daredevil keeping the streets clean type things or Avengers save the multiverses type thing.

I know nothing about masks, but it is by Magpie games, which means it is a Powered by the Apocalypse game. I personally do not care for those games at all. YMMV.

When I run superhero games I either use Palladium Games' Heroes Unlimited, or TSR's Marvel Superheroes.

Marvel also has a new RPG system called the 616 system. It utilizes 3d6 one of which is a different color. The upside to using this system, is it is currently in print... unlike the TSR Marvel system.

Heroes Unlimited may still be in print too. I know Palladium just reprinted TMNT & Other Strangeness. That is a spin off of HU and the two work well together.

Back in the late 80s into 90s there was a DC Superhero game too. I do not remember much about it, I think at only played a session or two of it. And I cannot remember who published it.

Mutants and Masterminds is another superhero game, I have never played it myself though.

Outgunned has an upcoming supes game that's cool!

Outgunned Superheroes