As you may know, Valve is working very hard at bringing the Windows games on Linux, their endgame being to conquer your living room with the ultimate Linux-based console.
The Steam platform has expanded in the last couple of years, over 1400 games being already available for Steam for Linux, while Windows has about 6400 games.
Despite this, from Valve’s statistics, the Linux usage is still about 1%, but we cannot know how precise is Valve’s data.
Popular games, available for Linux: Dota 2, Counter-Strike: Global Offensive, Team Fortress, Football Manager 2015, Sid Meier’s Civilization V and Garry’s Mod and The Witcher 3: Wild Hunt will also get Linux support soon.
As you may know, Valve has big plans regarding Linux gaming and is engaged in ambitious projects: SteamOS, a Linux based system for gaming, Steam Machine, gaming consoles that runs SteamOS and Steam Controller, a gaming controller for SteamOS and Steam Machine.