Dishonored

Arkane Studios' 2012 blockbuster, Dishonored, is a cult classic in the making. It's got star power, an innovative premise, and a gorgeous level of architecture to boot. Its sequel too looks just as good, taking the foundations of the first game and building upon them in a layered manner which is only bound to increase the franchise's success.
Dishonored's atmosphere and setting has clearly done a great deal to make the franchise resonate as well as it has done. Bethesda's involvement - a publisher synonymous with critical acclaim - probably helped a little bit too, but Arkane really do deserve most of the credit for the series' wide uptake.
Considering just how much the popularity of the stealth genre has waned in recent years, it's really encouraging to see a franchise that, having marketed itself primarily as being a stealth title, has managed to spawn such a successful IP. Here's to many sequels ahead!