I am the owner of GamingOnLinux. After discovering Linux back in the days of Mandrake in 2003, I constantly came back to check on the progress of Linux until Ubuntu appeared on the scene and it helped me to really love it. You can reach me easily by emailing GamingOnLinux directly.
Achron is a sweet time travel based RTS game available natively on Linux and has been for a long time now, they have a history of great support too with yet another update.
So Linux has a lot of games now, with plenty more still to come this year as it's early days yet, but I have decided to list a few you really need to keep an eye on.