New Game

I am going to become a game programmer, and i will eventually want to make my own games. I want my first games to be a sub game. But i don't know, should it be based on The Hunt For Red October, K-19 (not the movie), or should it be like starts off modern day and then a time portal opens and the sub gets transported back to 1939? Help me out, give me some ideas. We have creative modders here i am sure you guys will have a good idea.