You want to work on Formula 1 race car engines.
You need to start by mastering how to work on a simple car engines.
Then you need to master high performance engines.
Finally you can move on to the Formula 1 race car engines.
Back to the topic:
Games are computer programs, often with soft-realtime requirements, intensive graphics and audio and animation and network requirements, and so on. Or they can be as simple as a "choose your own adventure" stream of text blobs.
You need to start by mastering how to write simple programs.
Then you need to master more advanced topics. They may include networking, graphics, audio, and so on.
Finally you can move on to the big fancy MMORPGRTS you are imagining.
You transition up by taking on progressively bigger tasks. Exactly what those tasks are and how you decide to progress is up to you.
Edited by frob, 01 February 2013 - 04:36 PM.