A real good Captain America movie would be set in 95% of WW2, that way they can show what he meant to the troops, to the folks back home and to his enemies.
Only by showing what an icon and a hero he was THEN can it stress how much of a legend he would be NOW.
Red Skull would be good but i think he should be a creation of the real villain who works behind the scenes giving Hitler the machinery and super-troops needed to fight the Allies.
The real villain behind the scenes should be Arnim Zola (comic book fans take note), here is a master geneticist who can create monsters out of men and enhance men into super-troops capable of wreaking massive havok on the fighting forces in Europe at the time.
Zola is a villain who could have created fresh clone bodies in which to transport his mind into whenever he felt like it. Imagine it, this man could have been working behind the scenes all along over the years from various posts of power and then when Captain America is revived from the ice (in the second movie) then he could resume trying to destroy the one man he failed to in WW2.
Just my 2 cents, i think it would work.....Hey Avi Arad, call me on this!