A few months after Valve officially launched Steam for Linux in 2013, Gabe Newell gave his LinuxCon keynote crowd a bit of music for their ears. "It feels a little bit funny coming here and telling you guys that Linux and open source are the future of gaming," the Valve head-man said. "It's sort of like going to Rome and teaching Catholicism to the pope."

Linux gaming was by no means a new endeavor, but 2013 stands as a major year for the open-source platform's gaming prospects with Valve announcing Linux-based Steam Machines and the arrival of SteamOS. When we looked at the state of Linux gaming after its 12-month Valve anniversary, we found nearly 1,000 professional, commercially distributed games available as of February 2015. But this weekend there's an even bigger numeric milestone to celebrate according to the Linux site Phoronix—1,500 Linux titles are currently available through Steam.

Phoronix notes Steam has been adding roughly 100 Linux titles per month throughout the summer. And while the total number of Steam Linux offerings still pales in comparison to competing platforms—Phoronix cites Windows at 6,464 games and OS X at 2,323—the statistical growth in such a short period of time is undeniable. Anecdotal evidence supporting Steam's Linux gaming growth looks rosy as well. The five most popular Linux titles for Steam include major developer offerings like Counter-Strike: Global Offensive and Middle-earth: Shadow of Mordor (the rest of the top five according to Phoronix includes ARK: Survival Evolved, Team Fortress 2, and Dota 2). And this summer, a small indie game called Don't Be Patchman even became the first Linux-exclusive launch on Steam.

So while Linux on Steam hasn't been a perfect marriage to date—lack of driver support has been a continual issue, and the overall small market means little return for devs working on ports—there remains plenty for Linux enthusiasts to get excited about.

"At the end of 2013, when Valve released the beta of SteamOS everything changed," Che Dean, editor of Linux gaming news site Rootgamer, told Ars earlier this year. "After years of promoting the various Linux distributions, we had a major gaming company not just porting their games to Linux, but actually creating their own Linux-based operating system. It was an incredibly exciting moment and a turning point for Linux users."