Thanks for the thread, Thorangol.
My own list;
1) The combat. Very innovative and perhaps the biggest success of the Jay Wilson era. JW catches a lot of flak for his failures, but the effort and thought that went into combat dynamics is apparent and the result superb.
2) Audio and Visual; Terrific. The sound effects are an aspect that rarely gets mentioned, but if you play with 128 channels and have a decent sound system, the audio effects bleed through nicely. Graphically, smooth and appealing. Aside from Act 4 (which I found to be an eyesore), the tile-sets for most of the game is IMO the best looking ARPG I've ever seen.
3) I never thought I'd say this, but the itemization has gotten in a pretty good place. Some of the lone (non-set) Legs are really inspired and remind us of how far items have come since launch nearly 3 years ago.
4) Blizzard's continued support and passion to develop Diablo 3 well beyond it's release date. Though I must say, if they don't release 1 more xpac, I would consider it a crime.
The game overall needs one more big push from an xpac to get it where it should be, but there are many things to love about D3.