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If you're looking for a game on Linux that isn't available anywhere else, you're never going to find it.
Even if Linux sales are decent enough to make it a good target, the Windows and console markets are far larger.
It would never make sense to write a Linux exclusive game for money.
If there was an open source game that was only for Linux, people who like Windows would probably port it.
Those were the days when video drivers didn't support OpenGL very well. Those were the days when people wrote software graphics render engines in machine code. It was difficult to make games cross-platform.
Today writing cross-platform code is much, much easier.