I still think it's Walter Mashburn.  If Red John is so much like Patrick Jane, then Walter fits.  Both of them annoy Lisbon and Patrick likes Walter enough that they could be lifelong friends as Lorelei suggested was likely.  Walter's heart was broken when the woman he loved married Yuri which could have caused him to go crazy and become RJ.  Also, that would explain how he knew to kill Jane's wife to hurt him the most.

Watch the episodes with Walter (Redline and Red Hot), they're full of intense conversations between Patrick and Walter.  Walter says "you'll have to catch me" and that murder is easy if you plan right.  I could go on but out of all the suspects, Mashburn is the only one with the money, power, charisma, and intelligence to be Red John.  He constantly wears the color red and has a powerful/dangerous prescence.  Frankly, I just can't see RJ being revealed as a character that always wears a gray suit and seems to have a dull personality.

I really think it's Walter Mashburn.  He has the money and power to be Red John.  He has a dynamic personality and is likeable.  Red John has many friends and none of the other suspects seem to have it in them to draw people to them.  I can't see Red John being one of the boring characters that always wears gray.  I see him wearing red and having an interesting personality.

One last point:  it is going to look very unrealistic is Red John does not have money and power from a legitmate source.

i think is Walter Mashburn he has money, time, influence, he loves action and he bored easily also he fits the RJ clues
sorry if i made any mistake my english is not quite good