I thought that the second and third X-Men movies were really disappointing. I mean, I love the X-Men. I read the comics as a kid and grew up watching the tv cartoon. The first X-Men movie was OK; not really great, not terrible. Just decidedly average. Halle Berry was a disappointing Storm; Hugh Jackman was an awesome Wolverine. But from there, the movies got progressively worse and worse.
X 2? Utterly forgettable. I can barely remember anything about it, so many years later, other than the sense of disappointment I felt after watching it.
X-Men: The Last Stand? The best part is the beginning, when Cyclops is moping by the lake and thinks he sees Jean Grey...and Phoenix kills him. Seriously. That was awesome, because Cyclops is a boring git. But it's all downhill from there...too many characters, too many subplots, not nearly enough entertainment.
X-Men: Hugh Jackman's AWESOME so let's give him his own movie WOLVERINE!!!? Ok. I liked that one. Because it's Wolverine. It's not a good movie, but it's Hugh Jackman so I was good.
X-Men: First Class? Eh. Meh. The special effects in that one were AWFUL.