Hm, without thinking much I'd go with Kerbal Space Program, that's porbaly "game" I've spent most time with in ths decade...thing is, that's hardly a game, it's more of a sandbox space flgiht simulator.
As for "standard" game, I'd go with Dark Souls. That's only IP that got into my "Top 10 IPs with 3 or more entries" from 2010s.