It's crazy how well X-men 2 and even Spider-man 2 still hold up. I would actually put Blade 1 in with that group as well for films of that era that I would be willing to put up against any superhero film coming out today from either Marvel, WB, Sony, or Fox.
After BvS which I enjoyed a LOT. Enough to see multiple times I need to see X-men: Apocalypse myself. I rarely trusted film reviewers anyway but I took certain things into consideration but when things are hyperbolic or approach it that's when I shut them out completely.
Also the X-men going back to Marvel would be the worst thing. They don't have the time or resources to have that many balls in the air. Also you could kiss goodbye any serous themes with the X-men if they got them back. At least as serious as they honestly should be. The jokes, and I enjoy Marvel films, would be highly inappropriate. Even more so then they are now with some Marvel Studios films.