Why use Game Basic?
Simple! Every game that is released today has an engine behind it. Developing your own proprietary engine will take years, and then no one guarantees that your engine will be able to compete against the rest.
The market of 3D accelerators and API is undergoing rapid changes. Each month we hear about the new leader of 3D accelerators. If you have to spend your time testing your code on dozens of different 3D accelerator cards, you won’t have time to make the game itself. By the time you finish your game, the industry could look completely different. So you need someone else to take care of those details, and you've got to focus on your own development!