I saw this last night at a 7:30 show, and thought it was so much fun. I don't know where this ranks on my Marvel list yet and I'll probably need to see it a few more times before I will be able to rank it, but the FUN of this movie was just....immense. The characters, the dialogue.... My theater was crazy into it, too, which made it all the more enjoyable.
What I really appreciated was that there was absolutely NO weak link in the team - every character was awesome and well portrayed. Even Groot with his one sentence was sweet because of how many different emotions/context Vin Diesel was able to pack into that one sentence, said many times.
As much fun as I had with this movie, though, it doesn't touch Winter Soldier for me. That said, it easily topped the other two summer movies I've seen, DOFP and Maleficent. The pure joy while watching this movie blew me away. Heart, humor and characters that just pop.
This is Marvel's most fun movie since Avengers.