Well, you want to end up using a language like C, C++ and/or html. C is harder to learn than C++, but it is more powerful. If you are thinking about online games, try learning Java or Flash. You will need to get into college if you want to be hired by Activision, btw. Go for a graphics program in college, and physics/programming will benefit you immensely.
Right now, I highly recommend a program for you. Have you Ever heard of GameMaker? It is a free, very easy to use game creation engine that will let you create a simple (or complex) game within a couple weeks! It is difficult enough to be a challenge, yet simple enough that anybody can learn it. Making games on GameMaker will give you a good idea of the requirements for a game, and be a good steppingstone to a hard-to-learn language. Here is a link: http://www.yoyogames.com/gamemaker/windows
This will let you get a free, legal copy of the engine. I HIGHLY recommend you try it, it is perfect for individuals with your goals. Its parent site, yoyogames.com, showcases gamemaker games that have been created by people like you.