1) Comes in about around Iron Man 1 for me. Behind Avengers and Captain America 2 among the Marvel set of films. Maybe X2 and of course the first two Nolan Batman films are ahead after that among the superhero set generally.
2) Script is a little sloppy plotwise, kind of like Thor 2 was. They made up for it by being way funnier (Thor 2 did well to have little touches of this, so they're clearly learning not to take it that seriously). Avengers had a much tighter script and Cap had a much tighter plot and for a "comic book" movie an usually serious theme (similar to Nolan's Batman work or the first two X-Men films). This has a serious theme (dealing with loss), but it isn't as cleverly pulled off as Avengers or Batman Begins, say.
3) Marvel has really poor villains outside of the X-Men set and Loki it seems like (eventually Thanos). Ronan was a badass yes, but like the Winter Soldier or Kursed we have no idea who he is really and what or where his motivations of hatred come from (comic book fans do, but sometimes it needs to be spelled out in films). At least the Dark Elves and Hydra we got a brief and solid back story. Winter Soldier they get around to it, very late in the film. Ronan they do not. It is just assumed, correctly, his intentions are to destroy people and planets.
4) Did I mention it was funny? Other than Gamora, they all have plenty of funny bits (although she gets a random Kevin Bacon reference, so there's that). Including Groot. The sociopathic raccoon (Rocket) worked very well.
5) There are a lot of easter eggs at the Collector's.
6) I don't think the stinger scene at the end of the credits was worth much. It's very funny. But I don't see it developing into a film or more than a set of cameos like the persistent Stan Lee gag.
7) Update: This point occurred to me later, and probably shouldn't have. The film spent a surprising amount of time being actually concerned that people were dying in their quest to save a planet/city. Not merely saying "lots of people are going to die", but the "this actually concerned me that some random non-canon character Y was killed". Some of the other Avengers films have had this in some measure (Avengers touched on it a few times in NYC). But not quite to this degree. Considering the blockbuster action film of the modern era typically flattens half of a city (and presumably kills or maims thousands, if not tens of thousands), this was refreshing. It stood in stark relief to the terrible Man of Steel Superman film in that it actually felt like these guys cared what they were doing and we weren't just told they are "heroes". Show, not tell.