Games that support 21:9, and that would look awesome on my new monitor !
Cities: Skylines (2015)
Trine 2 Director's Cut (2012)
Metro Redux (2014)
Wasteland 2 (2014)
Ori and the Blind Forest (2015)
Kingdom: Classic (2015)
The whole concept for Kingdom is that of a horizontal scroll "RTS". Playing this on a widescreen monitor i must say is very handy and adds to the immersion. Galloping left to right and back in this gorgeous landscape is fantastic.