I think it depends on the type of game... It took me about a month to create my game, it's puzzle based, but the development time came from creating the art assets and balancing the gameplay. I just released it a few days ago, response has been pretty good - even without marketing and advertising. Naxus - http://www.nelsonhurst.com/games/naxus/ I've also worked with a team (12 people) to develop a FPS, it took us 9 months to create the first 3 levels - so it depends on the type of game you're developing. My advice is, when you decide to make your first game, don't be too ambitious, just finish a game with good effort to see how long it takes. Then you can plan your development time for future projects.