Doggystyle is nice when she has her head and shoulders way down and sticking it way in the air for the guy. However, I'd have to agree with below that the folded deck chair is the winner. I usually use my hands to hold the legs (right below the knee) and hold them wider rather than having them on my shoulders. But either way, it's a great one.
I love doggy as well as cowgirl. But I really love my sex life with my current girl because she is supper flexable and super kinky and she loves it when we do it with her legs behind her head, her back resting on a pillow and me driving into her with all my might. (deep penetration)
I do like doggy but to me it comes down to what position does my lady enjoy thhe most. I really like doggy where she is laying flat face down, legs together, butt slightly raised and me on top or behind her. I can go forever like that.