The only game(s) im aware of that did this is the Monkey Island series, and while it IS cool to play it with the new graphics, I tend to actually switch to the old graphic because thats what I remember and one of the things I loved most about the old games. But this was done 20 years after the original release of Monkey Island, and while it was a big undertaking, its nothing compared to the tast it would be to redo WoW. And is it _really_ necessary to rede the whole thing just to get new people on board ? I really dont think so.
One of the reasons they redid Monkey Island was to have an entire new generation enjoy these awesome games that we "old timers" played and loved when we were teens...But WoW is 5 years old...thats hardly enough time for a generation change.