First, open source is about being free to use as you wish, not about developing anything.
Second, how do you count? All the java/flash-based little games mainly targeted for mobiles and browsers, don't they run on almost every platform (except some consoles)? Are they really less than 10% of all games?
Third, as dominant as Windows is for gaming, there are (console) games that have never been ported to Windows. Furthermore, older generation of games tend not to run on Windows 7 conveniently or at all.
Linux cannot run all games, but neither can Windows, OSX, or consoles. A fact, but is it significant?
Entirely unrelated question: What does "not worth the hype" mean? I thought that "hype" means same as "much ado about nothing". If so, then by definition every hype is worthless to begin with. Where was that hype that made you inquire about Linux? What did it claim?