I love Far Cry 3 but it's not as playable as Red Dead Redemption.
I liked the territory system of FC3, but as soon as you take a section of the island away from the mercs, it basically becomes a big patch of nothing. I expected that they would employ the San Andreas system and have the mercs try and take back the land that they lost, but no attempts were made.
RDR, by comparison had enemies moving in and out of areas over and over again throughout the game.
