A proper lightsaber duel should be spectacular but grounded in reality. That may sound like a contradiction, but to me the TPM duel suffers on two occasions after the stabbing of Qui-Gon:

1) Maul and Obi-Wan finish a flurry and spin away from each other with a deliberate flourish, as if playing to an audience. Looks kind of nice, but really takes me out of the moment.

2) The ridiculous ending. As fast as they were duelling, no way a s-l-o-w move like Obi-Wan's takes out Maul.

On the other hand, the Anakin/Obi-Wan duel in ROTS was really good for the most part. I didn't like the locale (lava yes, lava PLANET no) and I thought the dueling while swinging from cable was pretty stupid. All either guy had to do was cut the cable.