Well, I guess the best way to sort this out would be to rule out all others, as Jane has done. And let me just say out front, I don't have any doubts on the fact that Patrick Jane is not Red John. The entire point of the show is about a damaged and angry man looking for justice. It would not make sense at all for him to be Red John. 

1. Brett Partridge- yes, he is sick and "ghoulish" and maybe even a little sadistic, but I think he is too young to be Red John. It says in the episode "The Red Barn" that Red John was a teenager in the 1980's at Ellington farm.Red John has been described in numerous episodes as a middle aged man- something Partridge is not. He can't be more than late thirties, which is the wrong age for Red John. 

2. Brenda Shettrick- there are a number of reasons why I think she isn't red john; she is now behind bars, and Red John promised the he would be killing often; she is a SHE, and all the named confirmed on Jane's list were male; she was sloppy and panicked in her final episode, something I do not believe Red John to be. 

3. Brett Stiles- hmmmm. he is a little trickier. But I don't think it's him. First of all, as with Partridge, he is actually doesn't fit the Red John timeline. He is too old. and although red john seems to be either a previous or active member of Visualize, Stiles is an integral member, a permanent masthead. Red John also likes to be close to Patrick, as another user mentioned, to watch him suffer. Stiles doesn't appear in the show often enough for this to work. Although I have no doubt he is somehow connected to Red John, i don't think it is him. 

4. Reede Smith, Sheriff Thomas McAllister- although creepy in their own right, both of these characters seem to vague to me to be Red John. Although we don't know who he is, I think he is now a relatively important member of Jane's life, and both these characters have not appeared often enough for this to hold true. 

Hang in there, I know its been long; There are three remaining names to be considered... Gale Bertram, Ray Haffner, and Robert Kirkland. There are actually three very viable suspects: They are within the age of about where Red John should be, are a close part of Jane's life, and there have been sizable hints given about each of their characters. It was hard for me to choose, but I went with Kirkland for a few different reasons. He, to me, seems the most interested in Patrick's life; he talks to Lisbon about him, and seems to actually have a keen interest in the case of Red John, something odd since Homeland Security doesn't usually handle serial killers. He broke into Jane's attic workplace to find out what he knows, and he seems to be pulling the strings a bit with Bertram. 
Anyway, yeah. I think Kirkland is Red John. Let me know what you think of my over done rant!