I'd say of all the people I've run into in the game, mbailey, thndregg and waystin are the three I'd give the nod to for best sport.
Mbailey, I first ran into him about two years ago, his spitfire vs. My FM2. We found each other three straight times over some base. I shot him down twice, once with a questionable front-quarter deflection. He had every right to be frustrated and complain on 200, but instead he sent me a PM complimenting me on how well I was flying the wildcat. He's always friendly on range, and an all-around class act.
I've known thndregg since I started playing, and he was one of the guys who took me under his wing to teach me how to fly, fight and bomb in the B-17. While I was never a member of the 91st BG, he always made me feel welcome on their runs. I remember when he scheduled a squad night at 1 in the afternoon so BQ 82 could fly with us from Iraq. He's always a great guy to run into.
Waystin is always friendly to everyone, and he will go out of his way to clear your 6 in a fight. He's fun to fly with, and great to work with on a command staff for scenarios.