Diablo is great for me because I get to fine-tune character builds while mowing down dozens of hapless NPC villains to get better loot to slaughter tougher NPCs by the dozens. It makes me feel like a bad-ass.
EVE is great for me because I get to fine-tune a character build while stalking my prey to get better loot eventually to face down more experienced players in single combat. It makes me feel like a bad-ass. Less frequently, but more intensely than Diablo for sure.
Reminds me of the saying at WotC about their main 3 game franchises back in the day:*
In Pokemon you and your friends summon cool monsters to kick each other's asses.
In Magic you summon cool monsters to kick your friend's ass.
In Dungeons and Dragons you and your friends find cool monsters and kick their asses together.
It's always cool monsters, you and your friends, and ass-kicking.
* back in the day is usually a Thursday. Statistics don't lie.