Debate Topic! Which Avenger is best? Go!

Here are the main three Avengers:
Iron Man
Hulk
Captain America

Sheild Members:
Hawk Eye
Black Widow

Gods:
Thor
Loki

Who is the best? If pitted against each other, who would win? I need these opinions for a debate with my friends, and I need as many opinions as I can get! Please, please, tell me what you think! :D
-Love, Blue Collar Doom!