This is a raging debate still in the SW community, so it does not surprise me that someone would disagree. Though as I watch the film, to me it looks as though Mace Windu genuinely gains the advantage during the lightsaber duel, which isn't a stretch because in combat Windu is Yoda's equal according to his official bios. It's only when Palpatine is on the floor with Windu's lightsaber inches from his nose, when Anakin rushes in that Palpatine really seems to get confident and feel opportunistic. But, regardless, Lucas has said that Palpatine didn't allow Windu to win, the character profiles for both Windu and Palpatine on the official Star Wars website describe Windu as gaining the advantage, and make no mention of Palpatine throwing the fight.
The book "The Making of Star Wars Revenge of the Sith" mentions that this particular scene was edited with the intention of making so that Palpatine did not fake his loss in the lightsaber duel.
I know Lucas has come out and said Mace Windu legitimately had the advantage, but feel free to watch the movie and have your own opinion. I still like to think Han shot first, so I get it.