This is pretty simple. I put together a few candidates who could play certain Avengers and you vote and comment. Have fun!
Ant-Man-Hank Pym
Patrick Wilson (Watchmen, The A-Team)
Nathan Fillion (Firefly, Serenity)
Tom Cruise (Minority Report, A Few Good Men)
Bradley Cooper (The Hangover Pt. I & II)
Matt Damon (The Departed, The Bourne Identity)
Matthew Fox (Lost)
Aaron Eckhart (The Dark Knight)
Simon Baker (The Mentalist)
Wasp- Janet Van Dyne
Olivia Wilde (Tron: Legacy, Cowboys & Aliens)
Paula Patton (Deja' Vu, Mission: Impossible- Ghost Protocol)
Eva Longoria (Desperate Housewives)
Rachel McAdams (Sherlock Holmes, Mean Girls)
Keri Russell (Waitress, Mission: Impossible III)
Morena Bacarrin (V)
Lucy Liu (Charlie's Angels 1 & 2)
Black Panther- T'Challa
Dijimon Hounsou (Blood Diamond, Gladiator)
Ms. Marvel- Carol Danvers
Diane Kruger (National Treasure, Troy)
Ali Larter (Heroes)
Yvonne Strahovski (Chuck)
Jessica Biel (Blade: Trinity, The Illusionist)
Alice Eve (She's Out of My League)
Luke Cage
Terry Crews (White Chicks, The Expendables)
Tyrese Gibson (Transformers trilogy)
Idris Elba (Thor, Takers)
Isaiah Mustafar (Old Spice commercials)
Spider-Woman- Jessica Drew
Jennifer Connelly (A Beautiful Mind, Labyrinth)
Odette Yustman (Cloverfield)
Olivia Wilde (Tron: Legacy, Cowboys & Aliens)
Megan Fox (Transformers 1 & 2, Jonah Hex)
Carla Gugino (Watchmen, Snake Eyes)
Sorry if I didn't put your personal pick for a certain character. There's only so many people I can list. I can't please everyone. But if you do think I missed someone, let me know below.