I'd suggest a rhythm RPG. An RRPG, if you will.

You're starting the thing from the back end a little bit. First try to make a game. Then ask if it's any worth. If you never made game before, chances are the first try won't produce no braid ;).

I'm going to make one. Still i have to see about licencing. 

" @Video_Game_King: What if I fail? D: I guess my biggest worry is making a shit game what gets published but no stars :P "

First off your going to want to learn object oriented programming(oop). Learning in C# would be best but you could learn in Java and transfer the skills(the two languages are very similar). Maybe take a few courses at the local University(first level courses are usually intro to OOP with Java).
 
Secondly you can make and test the game on PC for free without activating your 12 months. That 12 months is purely for deploying to Xbox, the code you write and test on PC should work with little to no modification to deploy on Xbox so there is really no point in activating it until you are ready for testing and deployment.
 
Thirdly XNA is a framework, not a game engine. So there is going to be a lot more programming and back end work then there would be on a different platform. There are many free(and great) game engines available for indie development, you can even get UDK3 for free(yes, that is Unreal Engine 3, as in the engine used for Mass Effect, GoW, and many other AAA titles). Though if you wanted to sell your work in these engines you usually have to buy an indie license.

Make a game and have Soulja Boy review it. 
 
I wish I had the skills necessary to make my own game.

I hate indie games and anyone that likes them

" I hate indie games and anyone that likes them "

Make a porno game.

You could make that Giant Bomb game all the peoples are clamoring for. It would have to be either a beat-em-up or an RPG, naturally, because both involve using a large amount of characters. The first one would be infinitely easier to program though. If you think that the subject matter is a little too obscure, remember: Nobody buys these games anyways. If you made a Giant Bomb themed game on the other hand, I would certainly buy it.

Make a post-mortem body treatment simulator.
 
Perform an autopsy. Reassemble and stitch up the corpse. clean, embalm and dress the corpse for a funeral. Cremation. Necromancy. Commanding your undead horde.
 
Not all in that order, obviously, as it would be pretty difficult to make a zombie out of pulverized bone fragments.