If you can stand the gameplay, at least 3. Warning, though, it's not a real first person shooter, and focuses on use of VATS, an automatic targeting system. (don't remember its gameplay well beyond that) If you don't think you could deal with that gameplay, go with New Vegas, the complete edition of which being $9. It still has VATS, but it's completely unnecessary, unlike 3. I never use it. Never played the turn-based 1 & 2, though.