Some were great (Captain America 2), some were good (Iron Man, Guardians of the Galaxy), some were fun (Avengers is not a good movie, but it is a fun one - pretty much the definition of a summer movie), some spent too much time building the universe for the movies to be good by themselves (Thor, Iron Man 2, Captain America, Thor 2), and some had people that could breathe fire (Iron Man 3: due to a scheduling error I've only seen the second half of the movie, so I can't really judge it properly). None were bad. At worst, they're boring (either of the Thor movies), but never actually bad.
I'm simultaneously a sucker for the shared-universe conceit (the second half of season 1 of Agents of SHIELD was a really fun ride, and I've spent far too much time googling Marvel lore to see what might be on the horizon) and glad when their movies don't focus on it. A big part of what made those first 3 I listed good in my eyes was that they worked perfectly well as stand-alone movies - there were things tying into either prior movies or the universe as a whole, but the fact that they were connected was never a crucial point that you needed to enjoy the movie. Thor and Iron Man 2 spent a ton of time making SHIELD into a thing, at the expense of doing much else with the plot. Captain America needed a way to get Steve and the Tesseract to the present and jumped through tons of hoops to make it happen. Thor 2...was really just kind of a mess all around, but hey, that Aether sure was a thing, wasn't it? I wonder if we'll see that again? (Poor Thor, he hasn't really gotten a movie that's actually about him yet: first Jane and SHIELD stole the spotlight, then Jane and Loki.)
But yeah, I'm generally a Marvel fan. I'd like to see the shared-universe stuff shift more to the small screen, where it has more time to shine, so the films have more space to tell their own stories, because when they do tell their own stories, those stories are pretty darn good.