Seems like Batman Begins had a huge amount of time, but X2 had just a little bit more of the same amount of time that First Class is going to have. Between X2 and BB, there's still not a huge gap in overall quality. I mean, sure, X2 is good, but Batman Begins is excellent. I guess my point is, if you have a good script and a good director, you'll expect to still push out a quality film--regardless of how much time you have. Whether or not that film becomes universally liked may have less to do with production time, but more to do with the story itself (i.e., Superman Returns).
After X3 and Wolverine, if First Class is anywhere near as good as X2, I'd say it'll be a huge step in the right direction.