Personally, My advice is too not start with a RPG cuz it tends to be repetitive, used alot and can't be finished quite easily. Unless its an old school 2D RPG in which case is fine. But I'd go for the old school FPS Horror games since it's easy to implement... You and Your friend should already know what engine you're gonna use and at least know the capabilities of it... AGAIN I SAY UNITY ENGINE! Cuz I endorse it ;3