Privileged individual becomes a castaway on an island far from human civilization. He learns to survive inhospitable terrain, avoiding predators using his wits and uber mad-skillz. He saves the life of a native who would have, in reversed circumstances, eaten him. Said native becomes a loyal friend and hunting partner. Castaway's distress signal gets picked up by renegades who also want to kill him, but they inadvertently provide him a ticket outtahere.
While the plot was predictable, following its precedent quite closely, the narrative in Riddick was arresting enough to make me forget the Crusoe tale. I only saw the parallels hours after. In Defoe's version, Crusoe had technological superiority on his side: guns against the cannibals' primitive melee weapons. Riddick has no weapons and has to improvise with materials scrounged from the landscape to survive the native predators and is vastly outclassed by the bounty hunters' weapons and gear.
That's it. Change one rule and the game becomes almost unrecognizable. Skillz, resourcefulness, terrain knowledge and psychology are Riddick's best assets. This is one movie in which you sympathize with and fear for the bad guys who have no idea what they are hunting. Riddick's mind games torment, frustrate and drive his hunters to breaking point, and watching the combined force crumble from its position of strength is what's fun about this movie.
This doesn't mean Riddick is invulnerable. If he was, it wouldn't be half as exciting to watch. He is mindful of an impending deadline, but rushes nothing. However, although he very carefully orchestrates every attack, not everything goes according to plan. Some nice 'oh, shit' moments keep us grounded with the presence of real danger for Riddick and friend.
I went in with no expectations, wasn't disappointed. The old classic stories were in themselves quite well written. A few cosmetic changes and an old story becomes new again.