I've noticed a bunch of little things, that when added up, make WoW a great game. We all know about graphics, sounds, jobs, races, etc.. but it's the little background things I'm noticing that are really making the game great.
For instance:
1) Have you noticed that the wolves will run around and attack the rabbits and rats that are wandering around? It's kind of fun to kill a wolf just after it's killed a rabbit.
2) Putting your name and job into the quests. Sure it's a simple programming thing, but it makes the game that much more immersive.
3) Starting each race in separate areas. This makes it so much cooler when you're in the human lands and you see a gnome or a dwarf wandering around. It makes it more of a big deal to see a lvl 5 Gnome wandering around in Northshire.
4) That you have to search out some NPCs. They aren't all in the same area. To find the leatherworking and skining trainers in Dolanaar, you have to search them. I found the enchanting trainer by accident when I was doing a quest (she's in Oracle Glade).
5) The quests are designed to progressively move you around the zones and explore.
What have you found/noticed that adds to the game?