Cap1 was my favorite Marvel movie. Cap2 might top it, but I'll need to watch them back to back to say for sure...they're definitely my top two. Iron Man 1 is probably tied at third with Avengers, which I'd follow with Guardians. GotG being in my personal top five...it wasn't so bad, now that I think about it, but it wasn't great (just like the first Iron Man, basically). Still better than the latter two Iron Men, both Thors, and any Hulks.
Re: Guardians, the cast was good. I was surprised at Dave Bautista's Drax...he did a great job on the role. But I shouldn't have been shocked, since wrasslers are already half-actors and half-jocks. Rocket wasn't as over the top as others have said: I thought it was well done, though Bradley Cooper was a little too shouty most of the time. Groot was well done, too: probably the best use for Vin Diesel anyone's ever come up with. Zoe Saldana was predictably good in her role: a bit more physical than usual for her, but she pulled it off well. Star Lord was played too silly, but then again that might have been the comic character's personality, too. It was annoying, though. It was good to see Michael Rooker back in movie work. I hate that I only know him from Cliffhanger, where he played a puss.
Ronan was an interesting villain (can't believe it's the same guy who's playing Thranduil in Hobbit), but based on what little I know from the comics, I think he was dispatched too easily, despite the difficulty they had in doing so. He's a recurring Marvel character, so I would expect him to crop up at some point in the future, maybe in Phase 3. Not enough Thanos. His bad bald daughter will be cropping up again, too.
Howard the Duck looked like crap, but much better than the 80's movie version.