Far Cry is an amazing game. I think it basically defines the FPS genre. You find yourself fighting your way through tropical jungles, before plunging into dark oppressive cave systems. Weapons and gameplay are amazing, I seriously recommend this game.
Enemies are responsive, but the AI is somewhat archaic by current standards (mercenaries will crouch behind a box and stay there most of the time) but they certainly are satisfying to headshot. In later levels the presence of mutants, called trigens, keep you constantly on tenterhooks. You never know where they'll come from.
With five difficulty settings, you'll never fail to be challenged. Whether you want a ‘peaceful tropical island stroll’ or you have a death wish, there's fun for the whole family.
This is my all-time favourite game, I've clocked it about five times on every difficulty, I seriously recommend you get it. Its so cheap, you really don't have a reason not to.