X-Men: First Class
Some pretty clunky acting, but as a whole its such a loving adaptation of the characters, it's a shame the subsequent films don't really get to expand on many of the characters.
Some of the CGI later in the film is rough, similarly the first version of beast's look is not the best.
Trying to recontextualize Mystique's nakedness is interesting but I would've preferred to ignore that of the original movies.