The Avengers movie follows and that plans are in the works for sequels to both movies, it's easier to accept Captain America as an extended introduction to the character setting up what his role will be in the series. If this were a stand-alone feature, it would be easy to criticize as coming off as rushed or not feeling as epic it could, but knowing there's more to come, I'm optimistic the intriguing elements presented here initially will be more fully explored down the road.
I think as long as I've known about superheroes I've known about Captain America and his status as icon, but my only prior exposure to the character was in the disastrous 1990 eponymous film and a few episodes of the Spider-Man cartoon I grew up watching when he made a few appearances. I never read the comics, but I knew he was a weakling named Steve Rogers given a super soldier serum in World War II, his arch nemesis was the Red Skull, and at one point he's frozen in the Arctic and thawed decades later, but other than that, I never really had much interest in him. He wasn't as cool as Batman, identifiable as Spider-Man, or unique as the X-Men; he just seemed like an outdated cornball Boy Scout of a superhero.
That all said, I enjoyed Captain America. I found the action scenes and special effects well done, the performances solid, and I'm intrigued by the different story possibilities going forward. Like Thor, this is less of a narrative than more of an introduction to the superhero so we know who he is when starts rubbing shoulders with Iron Man, the Hulk, and Nick Fury. It's not very ambitious in that regard, and there are few surprises, but as a superhero flicks, it's done with a simple, straightforward conviction.
My favorite moment in the movie occurs when Captain America and the Red Skull have their first confrontation at one of Hydra's bases. The two face off on a catwalk above a warehouse of weaponry burning down all around them, and Schmidt tears off the human mask to reveal the hideous deformed visage beneath. It just feels like such a big, important moment; I can just picture these two being sworn, mortal enemies for all time clashing in epic confrontations. Granted, nothing else in the movie approached this level of greatness, but like I said, I'm expecting this to be the first of many encounters between the two.
The movie also does well establishing the driving motivations for Rogers: first as the little guy with heart who never backs down and later, after the experiment is sabotaged, the guilt-ridden propaganda puppet who would rather be in the field than performing in USO shows. Like Iron Man, Captain America's alter ego is well publicized in his universe, but unlike Tony Stark, Steve Rogers is uncomfortable in the spotlight; he'd rather just do his duty. It foreshadows the inevitable clash of egos I enjoyed very much in The Avengers, and in nice touch, we learn it was Howard Stark (Dominic Cooper), Tony's father, who built Captain America's shield and assisted him on missions (by the way, the shield makes for some effective action scenes).
Captain America is not in the upper echelon of superhero movies, but it does its job. It introduces the captain and sets up future plot potential. On it's own, I probably would not rate it that high, but as a piece of the puzzle, it fits.