What is the most important aspect of Blizzard’s individual franchises?

What makes a Diablo game that, and not just a Warcraft game? Is it the lack of typical fantasy races and the grim, splattergore aesthetic? At one point, World of Warcraft had talent trees that were fairly blatant lifts from Diablo 2, but at no point did I mistake Westfall for Tristram. And neither game has ever even remotely felt like StarCraft, even though at one point both Warcraft and StarCraft were exclusively RTS games — but there’s an entirely different feel to a Zerg rush that doesn’t really translate at all into anything you’d experience in any of the Warcraft RTS games. Is it just the science fictional aspects that sets StarCraft apart? Because Overwatch is very clearly a science fiction game with giant robots and people who can teleport or affect gravity, and yet, it doesn’t feel anything like StarCraft.

There are of course elements that have strong similarties — Leah’s fate in Diablo 3 isn’t all that different from what happened to Kerrigan in StarCraft if you squint, and there are similarities between Widowmaker, Sylvanas, and the two we just mentioned as well. There are clearly themes that reoccur in Blizzard games, maybe sometimes a little too often. But there’s still a pretty fundamental difference between some of these games as well. Diablo games have — one would almost argue are defined by — a feeling of nightmare and a world on the edge of utter ruin that feels a lot more visceral… sometimes literally, there are actual viscera flying around… than anything in the other franchises. Not a lot of gore explosions in Overwatch.

So now I ask you — what makes these games unique, what elements are the most important for defining what is or isn’t StarCraft or Overwatch or Blackthorne? Both WoW and Diablo 3 have giant swords smashing into monsters but what makes WoW unique? What sets each of these franchises apart?