I still don't think it's a proper X-Men movie. It's just the one that has come the closest. It's still mostly Magneto/Xavier/Mystique origin. Yeah, other characters get development more than the other X-Men movies(gotta love that training montage), but they're still supporting characters at best, not the main focus.
It's so weird that a movie set 20 years before even the formation of X-Men and the single most inaccurate movie to the comics, is the closest to the spirit of X-Men out of the whole franchise.