Yoda is the most powerful on the list, but Dooku would win, he's smart he isn't the biggest target for either side and he's damned good. Not to mention that some would never dare to attack him, QGJ & GG probably.
Sidious and Yoda would both be the biggest targets and they would both eventually lose..
Mace would concentrate on Sidious, Obi Wan would want Vader who in his turn would want Obi Wan or Mace... Dooku isn't the highest priority on anybody's list.
Mace could never stop thinking about the deaths on the Geonosis arena, all caused by Dooku. He wished he had just turned around and killed him before dying himself (Shatterpoint). I bet Mace would let Yoda or someone else take Sidious while he took on Dooku. He also had some unfinished business with him (their duel before TPM).
Dooku had taken Anakin's arm and caused many deaths of his jedi friends, I think he would want to take him out. Obi-Wan was still his friend, I don't think he had an irresistable urge to kill him, but he did what he had to do. If he was to choose, he would definently take on Dooku I belive.
Obi-Wan would attack Dooku or Sidious I belive, he did not want to fight Vader.
__________________
Necessity is the mother of inventions.
(Don't be a pig, get an Icejaw sig.)
Wow, two many variables. How about we say they start out spread out from each other at least 1000 ft. from the farthest person. And we're assuming the Jedi can fight each other two, right?
If that were the case Yoda and Sidious'd both pretty much stay where they were and wait to fight till they needed to. Dooku, Luke Qui-Gon and Mace wouldn't rush off to find someone right away. Maul, Anakin, Grievous and Obi-Wan'd rush off pretty fast and'd run into one another. Lets say first Maul runs into Obi-Wan and Grievous and Anakin runs into Dooku. Maul and Grievous take on Obi-Wan. They are forcing him back when suddenly Maul betrays Grievous and stabs him. Grievous is out. Maul fights Obi-Wan. Anakin and Dooku fight. Anakin manages to overwhelm him like he does in ROTS. Meanwhile Maul gets in some good moves on Obi-Wan, then gets overconfident and loses (I assume this is ROTS Obi-Wan and Anakin).
Next Anakin meets Mace. A fierce duel ensures. Obi-Wan finds Luke. Anakin's already tired and Mace hasn't fought yet and kills Anakin. Obi-Wan's already a bit tired and Luke makes him a bit more so but he beats Luke. Then Obi-Wan meets Qui-Gon. While normally Obi-Wan'd win without much trouble he is tired and it's pretty close. While they are fighting Mace stumbles upon them. He stands still and watches. Obi-Wan manages to win and then Mace charges him and beats him before he has a chance to catch his breath. Next Mace finds Sidious. They fight. Sidious wins. After waiting an hour to catch his breath Sidious goes to find Yoda. They fight. On Mustafar this could be close but Yoda ends up winning.