Ain't that the truth. Seriously, I love Samuel L. in almost everything else he's done, but in the Prequels he just sucked all the air out of the room in every scene he was in. CGI Yoda was acting rings around him, for God's sake. Look at ROTS when Anakin tells Mace the truth about Palpatine. "A Sith...Lord?? Are you sure?" Hayden wasn't the one (or at least the only one) royally botching what should have been one of the most dramatic scenes of the trilogy. Leave him out of it, please.
Besides which, in terms of the wider Saga, Mace Windu has already served his purpose: The personification of everything that was wrong with the Prequel-Era Jedi. From his cavalier dismissal of Qui-Gon's belief the Sith had returned (and of Anakin himself, a dismissal which by ROTS had blossomed into open contempt); being too proud to admit the possibility that Dooku could have turned evil until it's literally in his face; his fancy gold-plated one-of-a-kind-purple-blade lightsaber, a most unbecoming weapon for a warrior who's supposed to be humble; his tendency to attack first and ask questions later (if at all), both in the Geonosis arena and against Palpatine...Mace made a very damning Exhibit A in Palpatine's case to Anakin that the Jedi HAD to die.