There is an interesting debate going on which is the better of the X-Men film series installments -X-Men 2, First Class or Days of Future Past. For my money-- It's "Days" that tops the films.
"First Class" director Matthew Vaughn
was all set to helm 'Days' but had to pull out due to his
commitments to Kingsman: The Secret Service. Bryan Singer stepped up to take over.
Just as Singer's involvement on 'First Class' is often
underestimated, Vaughn's contribution to 'Days' is as well. The surprise When
Singer came on it seems that he changed very little of Vaughn's plans for the
film--only tweaking a few sequences including the very cool sequence featuring Quicksilver (American Horror Story favorite Evan Peters).
Vaughn was asked by Collider just how much of his and Simon Kinberg's script for 'Days' remained on screen:
"I'd say 90%. I mean, we worked on the script
[Simon] Kinberg and I. It was a really tough decision for me, because I
pulled out just because I'd finished the Kingsman: The Secret
Service script at the same time and I was like 'My god if I don't make a
fun spy movie right now, somebody else's going to do it.' And I think
there's five coming out next year now. So we're going to be the first
of it, not the last. Bryan [Singer] did a few things, which I thought were genius that
weren't in my script. I had Juggernaut breaking into the Pentagon, he
changed it to Quicksilver and did that f--ing brilliantly, I have to
add. My idea was the Sentinels at the end, I wanted them to look like Mystique. I thought there should be thousands of mystiques attacking
them in the future. He changed a few more of the mutants, but it was
pretty close. Yeah, it was pretty close.”