For some reason, this came to my mind on my daily trip in to work and I talked myself in to Steve being a Hufflepuff.

Let me explain how I got there.

Gryffindor values courage, bravery, nerve and chivalry. Its mascot is the lion, and its colours are scarlet and gold. The Gryffindor motto is "Their daring, nerve and chivalry set Gryffindors apart". (wikipedia)

Hufflepuff values hard work, patience, justice, and loyalty. The house mascot is the badger, and canary yellow and black are its colours. The Hufflepuff motto is "Those patient Hufflepuffs are true and unafraid of toil". (wikipedia)

Yes, Steve is brave and has courage like no one else but those aren't what he's all about. Those are what people see. I think his heart is about justice (for everyone, mind you) and loyalty (to his country and to his friends). He works well with others and nows how to bring out the best of his entire team. He's concerned about civilians during a fight (did anyone see anyone else (other than Clint) worried about civilians?).

Steve is not about "this is the way we're doing it, team." He's very much about "how will we all work together? and what is best for everyone?"

I think that are all my points.