The only possibility that it isn't anyone on the list is Jane. It would make complete sense that he is crazy and is indeed Red John. The story is told from his point of view. Who says he is a reliable narrator? Makes me think back to the Usual Suspects when we thought we knew where the story was headed.
Also, found this interesting clip which just confirms my suspicions.
http://www.youtube.com/watch?v=l_CK_90hei0
