Oh Crowley definitely respects the Winchesters. Just remember: "Am I the only one who doesn't underestimate those denim-wrapped NIGHTMARES!!"
I loved that line! That's what upset me so much about Cas not going to Dean. Crowley knows they are a force to be reckoned with, Cas on the other hand seems to have a short memory, or the arrogance of angels.
I actually think Crowley would make a better Satan than Lucifer. All of the soft spoken "I'll never lie to you" vs someone that actually seems to enjoy the game. Yep, Crowley for the win.