I really really like the original, always have, but I think Criminal Intent might be my favorite, especially now that Jeff Goldblum is in it.. SVU is always solid. I even liked Trial By Jury.
I miss the old CI theme though. They started using the TBJ theme when they made the move to the USA Network.
This is the one they use now:
http://www.youtube.com/watch?v=giOPFIVItOc