In season finale we were given seven names, who Jane thinks could be Red John. I'm gonna tell my opinion about each of the suspects, but my memories of all of them are not complete or 100% trustworthy, so I may forget some important points and facts.
Brett Styles: was one of my first guesses for RJ when I started to speculate, who of the shown characters could be Red John. That's what I think ruins it: it's too obvious. Everything else is in order; Styles is old enough, witty enough and devious enough to be Red John.
Gale Bertram: was a suspect once before, but "dodged the bullet" when O'Laughlin emerged as RJ's man. For me Bertram doesn't seem as cold and crafty as I imagine RJ would be. I don't think RJ works at the CBI, and as a head of the CBI, so many minions he's had inside the CBI.
Raymond Haffner: he's quite smart, but maybe not smart enough for Jane. He also seems almost kind when Jane doesn't irritate him or he doesn't compete with Jane and the team.
Reede Smith: this one was very surprising and interesting. We know that Red John has at least a friend inside the FBI, but could RJ himself have a footing there? I don't know if Smith is old or clever enough to be Red John and he's been very minimal character, so him being RJ would be quite unsatisfying solution.
Bob Kirkland: he's got something going on and he's been an upfront character in this season. He's absolutely smart and mean enough to be RJ and a lot of things speak for it. He stole Jane's notes and killed Jason Lennon, who apparently was in contact with Red John. Having read Jane's notes he would know his suspects and could have predicted them for the Lorelai-video (but did Lorelai die before he stole the notes? if she did, then that theory is useless). He might be he best fit for Red John at the moment, but he also might be too obvious choice.
Sheriff Thomas McAllister: my first reaction to this name was: who the hell is he?? We've seen him in only one episode, where Jane fooled him six times in a row at rock-paper-scissors. In my opinion he's too random to really be Red John, the producers couldn't possibly do it.
Brett Partridge: he's quite young, but he sure is freekish enough to be Red John. He's also smart and works as a forensics tech, which could be a suitable job for a serial killer who enjoys watching his victims bleed to death. Conveniently he appeared in the season finale, and again I'm thinking: too obvious? But the more I think about it the more I see him as a possible Red John.
Honestly I was a little disappointed with the list and the whole finale. All suspects seem kind of lame choices, I would hope that none of them is Red John. I don't think it's Jane himself either but I hope it would be some remarkable character from Jane's past, like his father or so. It's probably not, because if I'm not completely wrong, RJ had killed many people before Jane's family and it became personal between the two them because Jane made it personal by joining the CBI. Anyway I think the producers should have handled the plot differently, now it has become a little stale and unthrilling.