First of all, A>B>C comparisons don't always work. The upper tier of the PT doesn't work this way (Sidious > Dooku > Mace > Sidious, as another example).
Now let's look at Anakin and Obi-Wan's fight.
- George Lucas says that they are not equal. He says, in the RotS commentary, that Darth Vader was superior to Kenobi in both lightsaber dueling and force power.
- Anakin wasn't as good as Kenobi in the emotions department. Kenobi had far greater control over his emotions.
Add this to the fact that Anakin was going through intense emotional anguish with Padme.
- Kenobi used a saber form (Soresu) who's purpose was to draw out fights. He basically stretched out the fight until Anakin did something stupid to mess up. Not only that, but his saber guard was never penetrated after becoming THE Soresu master.
- Alot of the fight involved lava skateboarding, climbing and balance-fighting. Kenobi was usually the first to run to these things
- Anakin comes close to wrecking him a few times. A hard kick to the chest comes to mind as well.
- Kenobi was his teacher and best friend. He knows him inside out.
- Anakin was winning the fight. At the line "This is the end for you my master" Kenobi is breathing hard and Anakin looks fine.
- Even with all these advantages for Kenobi, Anakin IIRC, according to GL, was going to win the fight if it continued.
Just my opinion though. It could very well be Anakin > Dooku > Kenobi > Anakin.