Some of y'all need to chill. Lets look at the facts here. Let me air it out real quick.
X-Men - It's not a GREAT film but it is okay and Singer had his hands tied by the studio. It was the first of its kind. Anyone wondering where all these comic book films came from, this was the first in the modern era. If the studio would have let Singer have full control who knows how it turns out.
X2 - As said, it's a good film and still holds up today. It's not The Dark Knight and its not as "fun" as The Avengers but it tells a great story and I feel it would be looked at more fondly if Singer had saw through his vision in part 3. The political content in the film is cool and the opening scene with Nightcrawler is still one of my favorites of any comic book film.
X-Men: The Last Stand - Singer had nothing to do with this. Rattner is a hired gun in Hollywood. He sucks. He took part of what Singer was going to try to do and not only completely fukked that aspect up but also added additional plotlines that made everything convoluted as fukk. I'm surprised Singer is still going to recognize this as part of the continuity but I can assure you most will probably be retconned.
Wolverine: Origins - Again this is not Singer's mess. It's so bad that Singer is acting like it doesn't exist and who can blame him. It needs to be forgotten by everyone.
X-Men: First Class - Singer was a producer here and oversaw the project. It's solid. It takes liberties with some characters and I felt they should have kept Havok out of it altogether but overall it tells a good story and the acting is great. When you have Jennifer Lawrence and Fassbender among others you know they are going to deliver.
Overall I would say Singer has done a pretty good job thus far with everything he's been involved with to this point. Are they perfect films? No. Are they better than some of the shyt that Marvel Studios has put out? Yes... people act as if Marvel Studios can do no wrong, they have put out at least a FEW terrible films now. They are not perfect either.
Singer probably does deserve to receive a little hate for what he did with Superman Returns but that's another story altogether. I didn't feel it was a terrible movie but nobody wanted to see a Donner era tribute at that point. It was time to move on from that era of Superman and start something new. That's the biggest mistake Singer made with that.