X-2 is not a sequel to the X-Men movie. X-2 is the X-Men movie, whatever came before was just an intro. That said, it's impossible not to compare this film with The Empire Strikes Back — darker, looser, more action-packed than the original, with an ending that's not so happy but nevertheless hopeful.
Wolverine is still the main star, as he well should be. (At one point Magneto mocks Logan by saying, "You always think it's about you!" Joke's on you, Eric... It is about him.") I don't know how Hugh Jackman does it, but onscreen he simply transforms into Wolvie — just the right hint of toughness, without becoming vicious; this is a noble savage cradling a tender soul. It's ironic that the main villain Stryker keeps calling Wolverine an "animal" — along with Nightcrawler, he's the most human character in the film.
Alan Cumming, as Nightcrawler, steals the show every scene he's in. I'm already practicing my impression: "Kurt Wagner. But in the circus I was known as The Amazing Nightcrawler!" The opening scene, in which Nightcrawler attacks the White House, is a fluid and breathtaking set-piece of action filmmaking.
Jean Grey also becomes a major player, with a storyline that deals with the evolution of her powers. Actually, everyone gets a chance to strut their stuff... we get to see Nightcrawler, Wolverine, Cyclops, Storm, Pyro, and Magneto explode in masterful displays of ability. We also get to see a lot more mutants from the comics. I won't name them here, the surprise of recognizing a familiar character is one of the great joys of the movie.
Unfortunately, Rogue is woefully underused — the Blackbird jet gets more to do! And we don't get to see her slink around in the leather costume she wears in the promos. Even her "romance" with Iceman leaves me cold. Well, it's not like the two of them can do anything, right?