Arguably Bryan Singer's masterpiece in terms of the X-Men series, X2: X-Men United is a fine good piece of comic book movie entertainment. Singer has proven that he can handle huge ensembles really well, and X2 probably has the best ensemble work of any of his films, X-Men or not. Between the Scott/Jean/Logan relationship, Wolverine and Stryker's history, the clashing Pyro and Iceman, Xavier's interaction with Stryker's son turned experiment, and the introduction of Nightcrawler, as well as the overarching plot with some fascinating social commentary, every character has their individual moment to shine and show their own growth as a character. That's ultimately the most important aspect of handling so many characters at once, and Singer nails it. The movie moves at a nice pace, slowing down for its character moments and speeding up during the action sequences. The latter are a blast thanks to solid choreography and visuals. The standout is the opening scene featuring Nightcrawler breaking into the White House: the breakneck pacing of the scenes lends to what is perhaps Singer's finest action scene, and that's really saying a lot considering his huge collection of them.
X2 is considered one of the best comic book adaptations ever, and for good reason. If it wasn't evident enough that Singer loves this lore and these characters, here's your proof.