Endless loot. Games like Diablo and Destiny that require you to grind for the perfectly rolled items suck me in something fierce. By rights it should be a boring mechanic because it's tedious, but when you compare it to "oh, I killed a boss or did a thing, now I get the exact same weapon everyone else has." There's no contest in my mind.

I enjoy cosmetics. I like to have a character look unique even if the character models stay the same. Give me clothes, pets, accessories, and even upgradeable and customisable strongholds or bases are great.

Definitely prefer real time combat to turn based.