I believe that the list of 7 is correct, I really do think that PJ was able to remember all the people he had shaken hands with, and then narrowed that down further. That eliminates all people not on the list

Bob Kirkland - He's dead. It's hard to be Red John when you're dead. 

Bret Stiles - He's a maybe, but I think it's unlikely that someone who already has his nemesis, the ying to his yang (Red John has his nemesis of Patrick Jane) would start up a cult. From what I understand of Red John he wants to play games with PJ, he wants to torment him. He wants to keep him running in circles. As such, I don't think he'd start up a cult. I also think he's too old.

Reede Smith - I think Tyger Tyger organisation is distinct from Red John. Maybe there used to be a connection, but I don't think there is at this stage. I think that the organisation has taken up part of what they know of Red John (Tyger Tyger poem) and used it for their own, in a salute to him. I think that they respect him and want to emulate him, but are not him. It could be that he started it, or that he used to lead it or something, but I think that either they're separate completely, or he has now left, and separated himself. As such, as Reede is clearly a member of Tyger, he's not Red John. 

Brett Partridge - I think he's too young. If PJ lost his family in the 1990's then Red John has to be old. I find it highly unlikely anyone under 21 would have committed the murder of his family, I also think that it would have to be someone of at least 25, but most likely 30. That makes Red John, now, about 45, if not 50. Too old to be Brett Partridge. 

Ray Haffner - I think him too violent and emotional and rash to be Red John, a calculated and careful man. I think he's more likely to be muscle for Tyger Tyger, which as I said previously, I believe to be different to Red John. 

Thomas McAllister - We know that Red John is a learned and well spoken man. Two things that do not seem apparent of Sheriff McAllister. I know voices can be put on, but it would seem to me that his has too much of a regional dialect, and too many colloquialisms. I also don't think he has the devotion it would take to be as thorough and brutal as Red John.

So, in the words of Mr Holmes, when you have eliminated the impossible, whatever remains, however improbable, is the truth. That leaves Gale Bertram. 

I don't think by any means this is a concrete argument, but I think out of the 7 it's most likely to be Bertram. I wouldn't be at all surprised if it's someone completely unexpected, and not even mentioned in the top 15 in here. But, I have to say, I think Bertram is the most likely. 

I think, that Red John is Bob Kirkland's TWIN brother. They said about him in the series for a reason. And even if Bob Kirkland said that his twin brother was killed by Red John, I think it is not true. There is a possibility that Red John was an old man, started to kill people long time ago (evidence is "the face" on the building in one of the episodes). If that old man died, Bob Kirkland's twin brother could continue the work of original Red John.
I am betting for Evil Twin!!!

P.S. I think Bob Kirkland thought about it, that is why he was asking everyone "Do you recognize me? Have you seen me before?" hoping, that victims would mistake him for his twin!

Okay, even if the man who killed the private investigator, it must be someone from the list. At the scene she answers the door, we can see the killer's shadow and we can see he has hair so we can eliminate Brett and Gale. When Cho asked, she said the man who she was working for was from visualize so my guess is Haffner. I'm not saying he's RJ, I still think this is a fake list. I think PJ is working alone, he can't trust anyone