I find it to be the most unique team superhero movie in that like the comics they break up into squads throughout the movie.
Frankly, it's my least-favorite of the films. Can't stand it. The entire film is supposed to be the search for Wolverine's past, more or less, and in the end, he learns next-to-nothing. I know it's supposed to be that he preferred not to know, but it essentially makes the whole film pointless. The narrative completely focuses on Wolverine and, aside from a small peak at Bobby/Rogue's life, devotes itself entirely to Wolverine in a film where he's at his worst, performance-wise, IMO.
I disagree and here's why...
The X-Men movies tend to have a main plot and a featured sub-plot for a main character, you ignored the main plot.
X-MEN:
The Main Plot
Magneto trying to turn the world leaders into Mutants.
Sub-Plot
Rogue being introduced to others of her kind and trying to accept what she discovers she is.
__
X-Men 3: The Last Stand
The Main Plot
The Government trying to suppress mutantkind.
Sub-plot
Jean returning as Phoenix and causing Havok.
__
X-Men: First Class
The Main Plot
Charles Xavier forming his First Class of Mutants to preventing Sebastian Shaw from starting World War III
Sub-Plot
Erik Lensherr hunting the Man who killed him Mother and becoming Magneto throughout
__
I haven't seen it but from what I know of...
X-Men: Days of Future Past
The Main Plot
The Future x-Men struggle for survival in a dystopian world and send one of their own back in time to prevent that future from happening.
Sub-Plot
Charles Xavier coming to terms with the loss of his friend, his siter and his legs to become the crusading Charles Xavier of the future.
__
And finally in reference to your post...
X2: X-Men United
The Main Plot
William Stryker attempting to use Charles Xavier to exterminate all Mutantkind with the x-Men joining forces with their Mutant enemies in a the-enemy-of-my-enemy-is-my-friend situation.
Sub-Plot
Wolverine searching for his past and deciding that upon learning small tidbits from Stryker that he prefer to embrace who he is now rather than learn of who he was.