I've always found Delta guys friendly.

I used to do an experiment with my crews when passing through Houston (we are Newark). We would make a point to make eye contact and say hi to every pilot we saw. The only ones who responded were other Newark guys passing through like us! This was at Continental Express, but it did apply to the few Continental guys we saw.

Doing this in Newark got a mixed response. I'd say about 50%+ responded back to us. I don't know what this means, but it was interesting.