I think what many crave from D&D is a shared story. The common experience that has bound the game across editions. This could be Greyhawk, Forgotten Realms, Darksun, Birthright, or some other setting applied to the D&D game, but it has to be meaningful and reach people.
A lot of people don't like the changes to the game. The fans are split about everything: what races belong, what classes belong, do the mechanics fit the game, are the settings still worthwhile? These are all valid questions. I have a hunch, and I don't have any idea if it's right... but I believe that many would find 4th edition more palatable if they had those common experiences to fall back upon. If many still had the Realms they loved, or at least something much closer to that, where might we be? If the designers had said "aw hell, you can keep the gnome!" how might some feel? I think the mechanics sell themselves once you play the game; they're very good. What I see turning many off is the strange look. Again, understandable. If I knew nothing about the platypus, and you told me it was a mammal, I'd laugh at you. So maybe the designers have underestimated the value of the shared experience and story, and the idea that "yeah, ok, we never used gnomes before, but they belong more than these half-devil dudes."
Anyway, back on topic...
The game is really missing content that fleshes out the character. Behind-the-screen mechanics are great, IMO. The races, classes, and powers all provide excellent foundations. I want more that expands on those foundations and helps to differentiate characters. There are a number of ways to do this:
- more meaningful feat choices in the racial and class categories
- more meaningful equipment choices across categories
- further applications of skills
- more books that add substantive content to the implied setting
All of these can contribute to characters that are unique and interesting from both a mechanical and story perspective.