Both of them.
Diablo II is a HUGE part of my Teen/early adulthood. Right now, it's flooded with bots (Not really new) but the community doesn't really feel like it's there any more. a remake would revitalize the game and a lot of my old friends would come back, even if only for a short while.
For Diablo 4. I'm a huge fan of the lore and I want to see the series pushed forward. I didn't get as much mileage out of d3 and I did d2, I'd like to see what they can do with Diablo 4 and see something new.