1. It's not Patrick. (Yes, it is really not Patrick)
2. It's not his father (RJ did this because he was "slandered in the media").
3. It's not a woman. (it should be obvious, but for example: RJ slept with Rosalind and I don't think she's lesbian)
4. We have already seen him.
5. A powerful and influential person.

So I'm going for Virgil Minelli and my secret favourite is Walter Mashburn.
Bret Stiles just seems to have a good relationship with RJ.

In the end the truth will come and set us free

In the episode where the two girls were kidnapped and one was killed, only Minelli knew the meaning of the name Roy Tagliafaro (cut iron). This, in turn led the team to kill the corrupt policeman who had bought Roslind Harker the toy elephant.

I think virgil minelli  is red john    coz red john's face reflection shown in "red john's friends" looks almost same as virgil's face

I chose Minelli because I believe it was supposed to be him in the first season ("HE IS MAN..." scrawled in blood by the victim of Red John on the bathroom wall).  However, the show became very popular, and people began guessing Red John was Minelli, so they had to change it.  They got rid of Minelli and began airing more episodes.  Fans were happy and the network was happy.  Then, in the final episode of season three, Patrick finally confronts Red John in the mall and kills him.  The voice matched, the mannerisms matched--it was Red John.  Fans were thrilled, but the show had to go on.  In order to have more successful seasons, Red John had to "survive," hence the "mistaken identity" in the mall of season three.  Bottom line is that Red John is whoever the network needs him to be in order to keep viewers watching. 

Spoiler:
Red John is Virgil Minelli (Gregory Itzin)

Virgil is in the series pilot, and is first introduced as Lisbon's boss, a career law enforcement agent. Virgil retires soon after. Virgil had been in his job at CBI for 8 years when he retires. Red John's "mistake" happened 9 years ago. Virgil has the contacts in his long career to allow for access to information to ongoing investigations. Virgil is able to find information that LaRouche is keeping secret showing that he still has current contacts and the willingness to skirt procedural and ethical issues to provide it to Jane.
He is never outsmarted by Jane in the manner that the rest of the CBI team seems to be.

Patrick Jane, Grace Van Pelt, Kimball Cho, Teresa Lisbon, and Wayne Rigsby: None of these can be RJ -- They all can be excluded because a RJ killing occurs while they are with someone else: you can't be in two places at once. Also, RJ can not be female: Recall the scene where Cho and Rigsby go to the convenience store to
find surveillance footage of a man buying a stuffed animal for Rosalind --a female would have been recognized right away, especially a tiny female -- RJ must be a male of somewhat average build.

In an interview, Bruno Heller tells us RJ is someone who has been in the series, and is a recognized actor (not a bit player). We are told this before any of the season 3+ characters are introduced, so it can't be the CBI director Gale Bertram, Hightower, or JJ LaRoche. The only other actor of great recognition introduced early in the series is Malcolm McDowell who plays Bret Stiles.

In Bruno Heller's original screenplay “The Network Draft”,  a character named "RJ Patel" is the CBI boss (renamed for the TV series "Virgil Minneli")  -- RJ, as in "Red John."

A lot of people feel that Virgil can't be RJ because of the episode where: Virgil takes the RJ case away from Lisbon and gives it to agent Sam Bosco.  RJ has Bosco's secretary, Rebecca, kill Bosco, which causes the RJ case to go back to Lisbon and Jane. If Virgil was RJ, why would he give the case to
Bosco, only to kill him a month later?  ...There are several reasons;
1. the investigation might have been going in a direction under Lisbon/Jane that caused RJ concern, so he pulled it away from them temporarily,
2. RJ could be testing Jane to see if he'd stick around with Lisbon and continue to solve crimes even if he was denied direct involvement in the RJ case,
3. thinking the FBI would might soon take over the investigation (or knowing that he was soon to retire), Virgil gives the case to Bosco to throughly (and selfishly) check to make sure his whole crime history is perfect. Rebecca is his inside spy.

I think its Minelli, they make it so obvius because they want you think there is someone else

I think going by the previous episodes Red John has to be somebody who's
- male, probably older: his voice is male and it was mentioned that he's a little shorter than Jane
- part of the CBI since he's always aware of what's happening and is able to hack into the system every now and then...
- someone with many followers (also in the CBI and FBI), probably a great hypnotist (incognito) as well
- someone with a major superiority complex... a father figure with a soft voice (Stiles voice is too powerful) and in a high position
- someone who knows what Jane and Lisbon share... why else would he ask for Lisbon's body in season 4 finale...
- someone who lives alone without family so he can go unnoticed
- someone whom Jane knows since he prefers to wear a mask during their encounter

Why did Virgil Minelli leave after Boscos murder... to go fishing? I doubt if a CBI chief could really relax or retire early after a highly geared-up life full of action... seems strange... when the lady who killed Bosco was being questioned Minelli was also present there and seemed quite nervous.. he probably poisoned her and was hoping she'd die soon. He pretends to be very straightforward and resentful of Jane's methods but I think he's just playing games with him and is in league with Bret Stiles. He actually tries to act stupid most of the time... I even think he faked his voice every now and then when he was CBI chief.