Luffy: NG. I don't think he believes in personal freedom or anything. He just wants to have fun and become the pirate king. I would say TN, except he is also a nice altruistic guy, thus, NG. He might be leaning towards CG, but that is more his personality than his morals.
Sanji: Surprisingly, LG. He has a code, and he follows it. Mainly it's about protecting women, but hey, I think it counts.
Usopp: CG. Plain and simple.
Zoro: Eh, LG or CG. He keeps to a code as well.
Nami: CN. She never really acts "good." She helps her friends, but that doesn't mean she really is good.
Robin: TN or NG. She never does anything chaotic, just the government deems it so.
Franky: CG. He wants to be allowed to do what he wants whenever he wants to. To quote One Piece wiki:
"Franky is strong-willed, slightly crazy, and free-spirited, with an often blatant disregard for rules. He does whatever he wants whenever he wants..."
Sounds CG to me.
Chopper: NG. He justs wants to be nice to his friends. He is kinda naive, so he hasn't really formulated opinions for himself yet.
Brook: Not sure. CG, maybe?