Like most people here I would have done things a little differently with the big RJ reveal...
I believe it was nearly impossible to give a satisfactory answer about RJ since in 6 seasons they haven't told us hardly any information about RJ. Without info we created this concept of RJ that we wanted to see resolved...
Here is how I would have liked to seen it go down
I would have put Partridge as RJ. I'm not sure his persona exemplifies the idea of RJ I had, but there were several things that would have set the table nicely for him to be RJ
First He's in the pilot, which means we've known RJ since the beginning. In his scene describing RJ painting the smiley face. His description of how it is painted has a flair to it. Also he seems to enjoy the fact that PJ knows it is a copy-cat. He seems to smile as PJ describes the horror of seeing the symbol and knowing you are about to see the dead body of a loved one. It would seem to fit with RJ to have him soak that up as praise, and it would seem to continue the plot and issues between RJ and PJ when PJ then immediately turns on Partridge and calls him irksome.
Second the only time he seems to be really nervous around PJ is when PJ walks into the hotel room which is a real RJ murder scene. Partridge acts weird and leaves quickly, which could have been played up as he was nervous that PJ would make some connection while he was there.
Third, Partridge's death was always shrouded in secrecy (which was the point for the writers) but I would have liked it if they had later explained that Partridge had not really died. Instead he used a look-a-like to try to throw PJ off his trail. He was aware of PJ's knowledge about the tattoo at this point, but his body double did not have the tattoo so he sanded the skin off the shoulder to make people think he was hiding a tattoo when in reality he was hiding the fact that there was no tattoo. Jane has had his suspicions up until this point, but it is confirmed for him when Cho sends the pic. Lisbon asks, "What does it mean?" PJ, "What do you think it means?" He smiles and walks out as if he knows a big piece of the puzzle. The mistake RJ made was removing the skin. PJ knows RJ would always be trying to make something appear the opposite of what it really is
With that piece of the puzzle Jane sets up the meeting at his house, fully aware that none of the 5 are RJ. Haffner, Stiles, and McAllister are informed once they arrive to the house that PJ is planning on using an explosion to draw the real RJ out. Jane puts the three of them in hiding to protect them from Tyger, Tyger and RJ. Bertram and Smith are the bait for the real RJ. PJ knows both of these men are bad men and deserve anything they get so he doesn't offer them the same protection as he gives the other three. McAllister was Tyger, Tyger, but had recently been very helpful to Jane, which is why PJ chooses to save him, along with the thought that he may end up being helpful in bringing down RJ.
In his final step to draw RJ out PJ uses the press to accuse Bertram of being RJ, which has finally put PJ a step ahead. With the police preoccupied with the man-hunt for Bertram, PJ returns to his house. He is standing in the room, looking at the RJ smiley on the wall. The door is shut. On the door is a note to RJ that is a quote of what PJ said about RJ on T.V. back when he had his show as a psychic. RJ opens the door. PJ says, "Hello Brett" without turning around. Partridge responds, "When did you know?" PJ, "As I went through the list of people that could possibly be the murderer of my wife and daughter I realized there was only one person that seemed so needy." RJ, "I guess you're right in a way. The only reason you are still alive now is because I needed you. I needed to feel the rush of having such a wonderful adversary. But now the game is over, and I have won. You have outlived your usefulness to me."
PJ slowly turns, "This was never a game for me. I have hunted you for the last ten years so I could stand face to face with you and have you look me in the eyes and tell me why you murdered my wife and daughter." RJ steps forward, smiles "Because you had to learn a lesson. You needed to understand that no matter how smart you are, no matter how clever you can be, you will never match me." As he finishes those words Patrick jabs a stun-gun into his side incapacitating RJ. RJ looks up at PJ who says "Now you will learn a lesson. You will know the pain that you have caused me." PJ then kills RJ by stabbing him to death. PJ takes his bloody hand and draws the RJ symbol on Partridge's face, turns and walks out of the room shutting the door behind him,
fade to black and roll the credits
that's just how I would have done it.