19. X-Men: First Class
The X-Men series was always a wildly inconsistent one, but when it was on-point it delivered some of the cinema's finest superhero flicks.
Out of the non-spin off X-Men movies, X-Men: First Class is easily the greatest. Why? Because, even though no actors from earlier films (save for a hilarious cameo by Hugh Jackman) are in it, First Class feels like the truest, most complete X-Men film of them all.
The X-Men series always stood out thanks to the way it mixed superhero action and political themes, but First Class offers by far the best tonal juggling act of the series. It blends epic action with potent social commentary better than any of its predecessors, and the fantastic character development, superb direction, brilliant acting and rich historical context further cement it as an all-time classic of superhero movie cinema.
It does suffer a bit from slow pacing and disappointing villains, but when a film is this thought-provoking, this fascinating and this goddamn entertaining, such flaws are easy to forgive.
It's also a notably strong prequel movie. Unlike (let's face it) most other prequel picture, this doesn't undermine the earlier movies and builds up backstory in a compelling, emotionally resonant way that actually enhances its predecessors.