Not only that, but it's actually going to be three years since release on Saturday! Honestly, it doesn't feel that long at all. I still remember doing a preview livestream before release on our Twitch channel. I'm still amazed Linux has games like this and with Surviving Mars due soon, I couldn't be happier.
It still has a rather active player-base too, with over seven thousand people currently in-game on Steam. Not only that, but the Steam Workshop is flourishing with many thousands of items like maps, buildings, mods and more.
To celebrate, Cities: Skylines is going to get a free minor update that will include a new unique Rocket City building called Xchirp Launcher, an astronaut Chirper, and a new free radio station - Official Mars Radio which will have a bunch of space-themed electro songs. The update will be out tomorrow, for those interested in that.
Side-note: I would be doing a preview livestream of Surviving Mars too, but the Linux review build has issues that will apparently be fixed in the release build that I reported. Hopefully I will have a livestream on the day of release!