Omega Man > I am Legend (the new movie). Although it would have been best if both had actually stuck closer to the novelette.
I have to say, for all its cheesiness, I really like Soylent Green from all of the Heston movies. Of course Ben Hur and Ten Commandments are classic (and what brought me to the Heston table), but his dystopia films are just so darn fun!
I would say that he starred in more dystopic future films than any other actor:
Planet of the Apes
The Omega Man
In the Mouth of Madness (sort of a dystopic future)
He was just so good to show a sense of passion, drama, and power. His voice was, like James Earl Jones, a force in itself.
"Neca eos omnes. Deus suos agnoscet!"
(Kill them all. God will know his own.)
-- Arnaud-Armaury, the Albigensian Crusade