1) First Class
Best story, acting, directing, and music. very rewathable.
2) x-Men 1
A classic
3) x-Men 2
A fun first watch, but lacks rewatchablity for me. great story. but not enough cyclops and too much wolverine.
and then the rest suck....
4) X-Origins Wolverine
A fun first watch. crappy story and lazy writing and cgi. still rewatchable because of my man sabertooth. still one of the best villains in this sloppy franchise.
5) The Last stand
a fun first watch, but still sucks. beast was the only good thing. this movie is still bottlenecking the franchise to this day. too much storm (i hate her) and wolverine. not enough cyclops and professor x. incredibly corny movie.
6) The wolverine
flavorless and boring. usually after i watch an x-men movie, I get in my x-men mood. I pull out my PS2 and play X-Men legends. might watch some of the classic cartoons. play some x-men video games on computer, etc. After the Wolverine, I did none of that. Even Origins and TLS Wolverine got me in the mood.