I have seen fair amount complaints about how Fox has handled the X-Men movies, so I have to ask, do you think Marvel would do a better job?
I'm not sure the X-Men fit the more light hearted tone of the various Marvel movies, I think if Marvel was making the X-Men movies, we may not have seen the genocide scene from Days of Future Past or the Holocaust backstory with Magneto. I also don't think Disney would have made an R rated Deadpool movie. I also think the Mutants struggle story would be hard to shoehorn into the current MCU, heck I don't it ever really jived with non X-Men comics in the 616 universe.
I think despite the movies flaws, Fox at least understands what makes X-Men works and some of the X-Men films are pretty good, unlike say Fantastic Four where Fox clearly doesn't why that works and should have sold it back Marvel back in 2007.
So I do think they are some trade offs with either Marvel or Fox making the movies, because they have different styles and different strengths and I do think there are things Marvel wouldn't want to do with the X-Men in film.
Besides people seem to complain about how Marvel handles the X-Men comics, so why do think those grievances won't translate to the films?