Hey, don't listen to the guy who talks about game maker. IT FAILS!!
If you really want to make a computer like the pros you need to learn and decide a few things.
1. WHAT YOU WANT TO DO
Choose what you really want to be doing. Do you want to program the game and make the code or do you want to design the graphics for the game. Or maybe you just want to think of the story line of the game and what features you should add. You need to know what you are doing. Most big and popular games have hundreds of people who worked on them. So if you want to make a huge game like that, you would probaly not want to make it all by yourself. However this doesn't mean that you can't make a game by yourself. Just make sure to start small. Over ambition is what causes 95% of projects to fail.
2. PICK YOUR PROGRAMMING LANGUAGE
If you want to make the game by yourself you'll need to know how to program. This is what makes the game work. If you don't want to ever get a job in game design you could use game specific languages like game maker. These are used only to make games. So it is a LOT easier but in turn they run WAY slower and are much less powerful than multipurpose languages. LIKE ALL big games, and even most small ones, use these big shot languages. For example, there are aAbsolutely0 Xbox, PS3, Wii, iPod Touch Apps, or even a computer game you'll buy at the store that are written in Game Maker which is only for hobbieists. (I do not know how to spell that) Some of these languages are Java, C, C#, C++, Objective C, XCode, and Python. I would rrecommendJava, C#, or C++. These three are the best languages because they are object oriented. Xcode is also good but is only used on Mac and is for making iPhone apps. C++ is my favorite and is what most big games are written in.
3. LEARN TO PROGRAM
Now that you've picked a programming language you need to learn it. This takes a LOT of time. So go watch about 1,000 videos on YouTube (trust me, I've done it) and read a couple of books. Once you've learned your language, you'll notice that you aren't making games yet. That is because you haven't yet learned any API's. These handle graphics output and hardware manipulation. Some popular ones for Java, C++, and C# are Allegro, SDL, OpenGL, and DirectX (DirectX is only for Windows). Once you know these you can make a game.
4. BECOME A GRAPHICS ARTIST
Yeah you can make a game but the graphics and game play are epic fails. First, you'll need to make some good graphics. I'd defiantly start with 2D. Some programs you can use to make sweet graphics are Photoshop and Gimp (Gimp = FREE!). It takes a while to learn to make good graphics, but that's just an artistic thing. If you fail at art you may not choose to make graphics and have some else do them. OR you may have chosen to only do graphics.
5. BECOME A GAME DESIGNER
Now you have good graphics and your game is playable, but it is kinda boring. That is where game design comes in. It mostly consists of endless hours of thinking about the plot, what features are in you're game, what the characters are like. It may not seem important but trust me IT IS!
There isn't too much you can do to prepare for this. You just need to be creative. But you should read a Book on it. I read Game Design Workshop by like Zimmerman or something and it told me all I need to know.
MY SUGGESTIONS
If you're making a game by yourself, this is what I recommend.
Learn C++. It's the best language for making games period.
Learn SDL and OpenGL. OpenGl is great for graphics, but it only does graphics. So you will also need to learn SDL for everything else.
Make 2D graphics. They are way simpler then 3D and you can still get great things out of them. If you don't already have Photoshop, get GIMP for free. To help you make graphics, check out a Wacom Bamboo pen tablet. It helped me a lot.
Do not be over ambitious. Start out with pong of something. Really. You need to get some experience under your belt before going and making a sweet Game.
Hope I help.
Jacob from Brad Hat Software