I dissagree with your dissagreement...
And you seemed to not understand what I was trying to convey the reason I say not a standard team is that they don't have a archetypal "hero" reason for saving the world mutants are thrust into the spotlight due to things out of their control. The X-Men are reactionary to the hatred the world has thrown their way not because all of them simply deciding to use their powers for the benefit of mankind just to out of pure benevolence. The life chose them they didnt choose it.
It was to stop their friends from being shot and murdered point blank range just for looking different they were built from intollerance not from wanting merely to fight crime. Even before most of the mutants get their powers they are usually outcasts still in some way.
Whether you want to except it or not is up to you but it's obvious that the tone is very diffrent than say JLA, FF or Avengers.
They are a task force who try to fight for their right to survive not just a standard superhero team.
Lookwise the only ones on the team that has stayed consistent enough to really say that black leather wasn't a proper portrayal is Cyc and Wolverine. Outside of that all the main team had black leather on before the movies introduced them. That's not to say I don't want more comic accurate costumes just that the ones we got weren't completely inaccurate.
EDIT: The original team also didn't have black but you get my point.
It's OK to disagree, like I said earlier.
Everyone knows that the X-Men haves slightly different motivation than other teams, but at the same time, especially in the beginning with Charles Xavier mentioning it several times, the X-Men are taught that they should use their powers for the good of all humanity while at the same time educating and teaching those with mutant powers how to use their powers and to be good examples of mutants to the world around them.
It's a variation of responsibility of power.
You say they are reactionary, and nowadays they admittedly pretty much are, but in the early books, I would argue that Xavier was really trying to be proactive and demonstrate that mutants should be embraced with the rest of society.
Again,it's OK to disagree, but I've been reading comics since the early 70s clear up to now, and X-Men was a huge chunk of that especially in the 70s 80s and early 90s. And I will disagree with anyone who tries to say that at the heart of their team the X-Men are not trying to make the world a better place for everybody, because they are.
Of course they are not like the avengers and no one has claimed otherwise, but like I alluded to in my earlier statement, many teams have different core properties like the fantastic four is a family of explorers, and the avengers are simply a straight up fighting force, and the X-Men is a school, but one motivation that they all do share is they are a team that has as one of their main motivations the betterment of the world at large.
And again as far as tone, no one is saying X-Men would have the same exact tone as Avengers, what I'm talking about is that I think Marvel Studios would be able to make a sufficient tone that would fit the X-Men and I haven't seen anything to say that they would not. I'm sure they would as they are connected marvel which is the group that makes these books in the first place.
As far as the black leather costumes, I disagree with that as well, except for Storm the other X-Men like Wolverine, Colossus, Rogue, whoever they didn't wear the black leather until he came out until Morrison started that on his run of X-Men and that was after the movies. Cyclops might be the only one I'll give you only because his costume a lot of times simply basic.