Feature list
Challenges

Challenges are the equivalent to Achievements from Diablo 3. Players get a unique title for each Challenge.
Customization

Characters can be customized more than ever, with different body sizes, eyes, hair, tattoos, and scars.
Cutscenes

Real-time cutscenes will feature your unique character's look inside Blizzard's famous cinematics.
Lair scene

Players can customize the look of items in the Lair Scene with dyes and see how cosmetic items look.
Leaderboards

In addition to a "top players" list, Diablo 4 will feature a multitude of fun and challenging leaderboards.
Nonexistent

While Diablo 4 has tons of new features, it won't have everything, like an auciton house and player housing.
Most full-featured Diablo yet
Diablo 4 will bring back the most popular features of past Diablo games (e.g., achievements, Hardcore Mode, seasons), while introducing radical new ones (e.g., mounts, open world, real-time cutscenes, weather, and world bosses). Blizzard says Diablo 4 will feel more like Diablo 2 than Diablo 3, with a darker and more medieval feel. The game's meta will also change dramatically with each new season.