To my recollection, Captain America has been portrayed in live action by three actors before this film.
The first version, a 1940's serial starring Dick Purcell, was a truly hideous adaptation, with a different backstory, motivation, and identity. He didn't even have a shield.
The second, a pair of 1979 TV movies with Reb Brown, weren't MUCH better, although they at least got his name right.
And the last was the 1990 Matt Salinger pic, an utterly forgettable piece best known for the costume's rubber ears.
I believe I can say, without fear of contradiction, that this film blows them all out of the water.
The plot is familiar to anyone with semi-decent knowledge of the character. Scrawny loser volunteers for a test, gets turned into a Super Soldier, fights Germans, and helps to save the day. The basic outline is the same, and while there are some twists (including a rather nifty take on Bucky Barnes), there are no real surprises.
This isn't a drawback, although it may sound like one. The broad strokes serve a very useful purpose, in that they allow the story to move. With the exception of one drawn-out sequence involving the USO (which, I suspect, drags on purpose) the plot keeps moving forward, sweeping the viewer along until the final confrontation.
It's not a breakneck pace, mind you. There's breathing room, but they flow organically from what proceeds to what follows. There's little padding in the script, and much to enjoy. I will admit that it stumbles at the very end, lacking a final punch to close the movie off (unless you count the stinger/teaser at the very end of the credits), but not enough to spoil the film.
The real strength of the film, however, are the characters. Naturally, Steve Rogers is the heart of the film (in more ways than one) and Chris Evans' performance will amaze a lot of folks who only know him as Johnny Storm or one of The Losers. The wisecracks he's best known for do not make an appearance, and are replaced instead by an earnest desire to do one's part to defend the world. It's very easy to forget who he was in other films, when who he is in this one rings so true.
His polar opposite, of course, is Hugo Weaving as the Red Skull. I found his performance surprisingly low-key, considering the character is truly mad. Perhaps it is because his is the insanity of the fanatic, not the lunatic. He truly sees himself as the bearer of a great destiny, and (as one character put it) he has the power to actually achieve it. And that makes him truly scary.
Hayley Atwell's Peggy Carter serves an interesting role as the love interest. It's not quite the same role as Green Lantern's Carol Ferris, or Thor's Jane Foster, as their closeness grows during the story, instead of taking place mostly offscreen. It's fascinating how their scenes together fit so well into the storyline, without feeling like an interruption.
Most of the other characters, like Stanley Tucci's Professor Erskine, or Tommy Lee Jones' General Phillips, are given little to do, but feel real in their brief moments to shine. Jones especially gets a few great lines in (including a lovely callback to the Hydra oath that seems so obvious in retrospect I'm amazed it's never shown up in the comics). Another character that was a pleasant surprise was Howard Stark (Tony's father, and apparent role model). Dominic Cooper channels just enough Robert Downey Jr. to make the relationship clear without turning into parody or pastiche. And, in his own way, he's as much a hero as his son.
That being said, one character I found a bit one-note was Sebastian Stan's "Bucky" Barnes, here recast as Steve's best friend from Brooklyn (and an unofficial replacement for the WW2 era Nick Fury). He was believable as "the hero's buddy", but I'm hard pressed to remember anything distinctive about him. He could have easily been another one of the Howlers.
(Yes, they are in the film. Yes, they kick butt. And yes, Dum-Dum Dugan shouts "WA-HOO!" at one point.)
But that still doesn't detract from the strength of the film, an old-fashioned adventure film that hearkens back to the director's The Rocketeer, which coincidentally reached its 20th anniversary this year. In fact, I'm half-certain that Rogers wears that hero's distinctive leather jacket at one point, although I may be wrong.
There are, however, little details that I know are in the film, including a lovely Easter egg in the form of a red-suited "synthezoid" in a tube at the 1943 World's Fair. The chronology may be off, but the cameo is perfect.
If one desired, one could quibble about some clunky dialogue, cliched characters, or logical leaps in the plot, but in the end, it really doesn't matter.
Captain America is a fun movie. And worth watching.