Far Cry 3 has skill trees rather than the more traditional RPG elements in Fallout (attributes, ability to role-play, etc.). This game is more akin to Borderlands, really. You have no control over your character in a story-telling sense and you can customize your character by unlocking new skills upon level up. The actual numbers for health, armor and damage are hidden and you don't loot weapons the same way you do in Borderlands, but the skill trees and weapon selection are really reminiscent of Borderlands to me.
The best description I could come up for this game would be a cross between Borderlands, Skyrim, Battlefield 3, and Red Dead Redemption: the kind of RPG elements of Borderlands, the weapon customization and overall graphical style of Battlefield 3, the crafting and open world of Skyrim and the hunting of Red Dead Redemption.