It'll take a lot to screw this up: Iron Man, Captain America, The Hulk, and a handful of other extremely cool heroes in uniform, all blowing things up together wonderfully. Watch this trailer in HD... now.
It'll be tough waiting until next year for this, but until then, I'll keep this incredible line by Iron Man in my head:
"Big man in a suit of armor. Take that away, and what are you?
"Uhm, genius, billionaire, playboy, philanthropist..."
Other points of awesomeness:
Sammy Jackson's eyepatch
Everything Tony Stark will say
Thor looking out of place
Car explosion chain reaction
Captain America eating sushi off his shield [Apple]