Options.
And I'm not talking about 'a-dozen-third-party-books-that-will-eventually -come-out' options, I'm talking basic, my-character-shouldn't-be-exactly-the-same-as-every-other options. My biggest grip with the game is that while the wizard may have an at will magic spell, there is really only a couple of at will magic spells to choose from per level that a worth a damn. The path 'builds' are fine but I just want to make my character my way, picking the skills, feats and the like that I think will make a cool character. It's how I play WoW too, or try to, which is probably why I'm not great at that game. 4E feels like that to me. If I don't take one of the very few possible abilities, or the right ones, and build my character the right way, my character isn't cool. I want versatility, not necessarily maximum effectiveness.
I love Angrydad's description of the other major element of the game that bugs me but just not having every third ranger being a copy of the first would be awesome.
AD