I need to find a extremely good video game.?

So me and my brother are looking for a good video game to play extensively. He wants wants a first person shooter, but i would like an RPG. We both decided that an RPG would be okay as long as it had good battle sequences. We both want this game to either be extremely long or to basically never end. Please can you guys help us. We are looking for an extremely fun game to play together. Thank you.