I wouldn't say unpopular, just relatively new. The only games I can think of running that engine haven't released yet -- RSI's Star Citizen and Amazon's Crucib

I wouldn't say unpopular, just relatively new. The only games I can think of running that engine haven't released yet -- RSI's Star Citizen and Amazon's Crucible. Star Citizen's long development cycle and various funding sources have been well-documented, and it still lacks a concrete release date; on the other hand, Crucible comes out next week.