One of my favorite games of all time, Command & Conquer has been recreated in HTML5 by Aditya Ravi Shankar. Just because it is in HTML5 doesn’t mean that the game is missing anything. The music, and even videos are fully intact.
GOG.com has 26 classics like Syndicate, the Ultima series, Alpha Centauri, SimCity 2000 and so many more — many of which are optimized for both OSX and Windows — DRM-free and half price! Getting all of these games might be a bit much...