Matthew Vaughn had a much better grasp on every character he used and... as far as I can tell he would have a much better grasp on... anything to do with the plot or scenes as seen in the film. What I'll give it is that you can still see the elements that made first class work, that being the angst ridden brolationship between Fassbender's Magneto and McAvoy's Professor X, but it didn't do much with it.
I actually liked Singer's earlier outings, even when you look at them in hindsight, but what really goddamn kills this is that it completely lost its sense of "fun". You know, that thing that people have sometimes to combat the inherent potential for all of them to become psychological wrecks at the drop of a pin? Despite suddenly manifesting some DEM, always nice, I feel like Kitty and the rest of her group were terribly underutilised... in that I'd like to have seen a full film with just them and I can't see it being any less entertaining than what we got. If only because of infinite potential Blink's ability adds to any fight scene when compared with... oh... I dunno... claws?
What actually did bring the film down somewhat for me, despite all criticism it was fun to see, was how Singer appears to have completely trashed First Class and anything that could have done. Maybe there was some word from on high about this but I just get the feeling that it was less professional/monetary pressure and more Singer petulantly guarding what he considers to be "his" franchise.
Oh that and the fact that the plot basically boiled down to "Isn't Raven hot? I mean damn!". It was equal parts amusing and silly to see herself and Beast share meaningful looks _every_ time they shared a scene and it didn't help that both of our male leads who didn't already have a thing for her daughter clearly had a thing for her.