The Best:
Civil War (pits the team against each other instead of a formulaic one-off villain)
Avengers (first majorly successful crossover on screen. amazing action and scale)
Doctor Strange (psychedelic trip, interesting use of infinity stone and final battle)
The Winter Soldier (subversive villainy, emotional resonance, political statement)
Incredible Hulk (brutal brawling not seen in many other MCU films, doesnt feel like the rest)
Iron Man (first of the best, solid impactful origin story, doesnt feel like the rest)
Guardians of the Galaxy (surprise, proof anything goes with the right character development)
The Rest of the Best:
Age of Ultron (muddled and way too fast paced, formulaic villain)
Ant-Man (silly and mostly irrelevant to the universe at large so far, formulaic villain)
The First Avenger (awkward and too patriotic, weak villain)
Iron Man 2 (meandering and uncertain, under utilized villain)
Iron Man 3 (swing and a miss, twist was lame imho, eye-roll villain)
The Dark World (forgettable, too much human focus and weak plot, under utilized/formulaic/weak/eye-roll villain)
Thor (boring, not enough action and too much human focus)