Another Free to play game that I myself put about 15 hours into is Trove its build in the style of minecraft but its not really like minecraft think more Diablo loot fest with with classes you unlock through leveling multiple skills and professions, The Dev team has been doing great with tons of content updates and lots of events for you to do.
check out the steam page right here and remember even if you dont like minecraft give this a chance since its more of a FPS diablo game its worth the download and its Free.