D4 is an exercise in how a lot of effort and a lot of thought can go into something and result in a game that's inferior in the important ways (is the game actually fun to play, is progression fun and rewarding) while also being technically superior to its predecessors -- the game looks amazing, the engine is fantastic.

I'm playing it with my wife and it's just not very fun yet. It reminds me of grinding levels in classic WoW, but without the benefit of getting new skills and feeling more powerful with the levels. I'm hoping that after some patches, seasons, and expansion packs that it gets to be a little more fun, but right now they've made leveling so slow and so inconsequential that the game is just a repetitive slog. You're not getting any new skills past level 50 but it takes absolutely eons longer to go from level 50 to 100 than it did to go from 1-50, all areas in the entire game except for nightmare dungeons are level scaled so you aren't actually getting any more powerful with each level, you're just watching numbers go up while killing exactly the same things in exactly the same way you have been for the last 50 levels.

Appreciably, Diablo 3 was kind of crap at launch as well and it wasn't until they removed the RMAH, added a new class, added adventure mode and bounties, and added a lot of seasonal content that it fleshed out to being as fun as it is now. I'm hopeful that D4 eventually gets there but man it's just not the fun I was hoping for presently.