NOTE: This is long. Read only if you don't mind long posts are you just like more fire for your debates.
Master, therefore RotS, Obi-Wan Kenobi and Count Dooku/Darth Tyranus vs Darth Revan. Let's do some dismantling, but we'll only deal with what could be a factor in physical combat (Revan and Dooku's respective talents for inspiring loyalty and gathering allies aren't valid, for instance).
Master Obi-Wan Kenobi
- At this point in time, Obi-Wan is a member of the Jedi council on Coruscant. From this alone, it's safe to assume that not only is the Force flowing strongly through him, but he has also attained an immense degree of control.
- Obi-Wan is completely trained and obviously more than capable, however, his knowledge of the Force, as I understand it, is pretty standard as far as Jedi at the time go. There's nothing special here; no ancient or forbidden knowledge, no special or unique Force skills/powers, etc.
- Obi-Wan's fighting style with a lightsaber is based on Form III, which is primarily defensive. For a Jedi who undertook training during an extended time of peace, this is perfect; it's very Jedi-like to focus on defense and the preservation of yourself. It's an incredibly useful style of combat when your enemy isn't using a lightsaber him/herself, but in a dual, it's not terribly advantageous.
- Master Kenobi contributed highly to the Jedi's strategies in the Clone Wars and became legendary for it. He's also constantly level-headed and collected, so I'd place him as a 'master tactician'.
Count Dooku/Darth Tyranus
- As a Sith Lord, obviously Dooku's got something going for him over most of the Force-user population. He was trained by Yoda, which might mean something for anyone who thinks Yoda is the greatest ever. The Jedi archives list Dooku as formidable, and if the Jedi themselves are going to say he's a threat, well then dammit, he is one. He challenged Yoda.
- Dooku was trained by Yoda, who is obviously well-learned and wise in Force-related knowledge, but beyond that, I think his training is pretty standard. He may or may not have received much additional training from Sidious, but I would say he had, since he was throwing Force lightning around like it was no one's business.
- Dooku's lightsaber style of combat is considered to be 'old school', but it's served him well. He's considered to be incredibly skilled with a lightsaber, better focused and skilled in saber-on-saber dueling, and between him and his teammate, he's the better duelist. He held his own against Yoda. That crap about Yoda not trying to kill or hurt Dooku is moot here; there's no way you can't kill or at seriously maim someone with a lightsaber, and Dooku kept Yoda from doing that.
- Dooku wasn't known for being much of a strategist. Rallying troops and allies, sure, but as a tactician in itself: nothing particularly special or dangerous. All of that 'Well, he manipulated stuff, blah blah blah' doesn't matter, because it's all just stuff Sidious told him to do anyway. Of the two teammates, Obi's the better here.
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Darth Revan
- In terms of raw power and control, Revan is beyond the other two. Revan's mere presence overwhelms other Jedi (note, Bastila, and she herself was considered to be unusually strong) and he was also a Dark Lord of the Sith; the only true Dark Lords we know are big-bads so there's something here in itself. Intensely feared by the entire Jedi order, able to power and control the Star Forge, and draw from Malachor-I-forget-the-number without his own will breaking, we're talking some serious power. He even regained master of his power quickly, in a matter of weeks, even after it had been completely wiped.
- Training wise, I can't say that the KotOR era's Jedi training was any more effective than the prequel trilogy era, however, we do know that Revan was enthralled with gaining knowledge, no matter how forbidden, and that he learned from many different sources. A text-book geek who could do everything he learned.
- Lightsaber-wise, Revan comes from a period where Jedi and Sith often clashed with lightsabers -- a far cry from the movie period, in which even during the resurgence of the Sith in the Clone Wars, no Jedi expected to be fighting against another lightsaber. We also know Revan was incredibly skilled even for a Jedi of this time period, because he whipped a lot of ass. He also has Tulak Hord's holocron, which is pretty much a manual to "How to Be the Best Duelist... Ever".
- Strategically, Revan is almost the sole reason why the Mandalorians lost their war with the Republic. He was tactically devastating and even against the Republic itself, his only slip-up was in his underestimation of Darth Malak.
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In the end, I'd have to say Revan wins. It's not unusual for a single individual to win in a saber duel against two opponents; we see it often in the movies itself. Dooku is a prime example. Obi-Wan Kenobi has no clear advantage over Revan; if it weren't for his ability to strategize, he'd be simply out-matched and would only serve as a distraction for Dooku. Dooku himself can't match Revan in sheer power, knowledge of the Force, nor in tactics, and thus we'll have to go on his ability with a lightsaber. Dooku, who is far more knowledgeable in the act of fighting against another lightsaber, might be able to give Revan a hard time, but in the end, I think it'd be Revan who'd win their duel. Skilled on his own, vastly more experienced than even Dooku, and a learner of Tulak Hord himself, Revan's just the better.
Since this is the two at the same time against Darth Revan, I'd say it may give Revan a hard time, but in the end, when the dust has cleared, Revan, albeit perhaps injured, will still be the victor.