I think that many tennis fans immediately were captivated by Federer, and if they were younger and Fed was their first tennis "idol", it took them a while to even accept that anyone could challenge, let alone defeat, their idol. And with Fed (and I still like him), there has always been an air of mythology about him. So, it took many true-blue Fed fans a while to accept Rafa. if they've done so. But for the most part, Djokovic, who emerged a little later (and was somewhat brash at the beginning), has always been the third wheel - which has been exacerbated by how respectful a rivalry Rafa and Roger have had. Interestingly, I gravitated to Fed the first time I saw him play, but even more so to Rafa when I first watched him and he practically burst off the screen into my living room.
Novak has also been a little more of a process for me, and now, he's my co-personal-favorite with Nadal. In many ways, his personality is more genuine than the other two, but his game is more subtle. The usual cliches come to mind: not as elegant as Fed, or eye-poppingly dynamic as Rafa. But what you get is consistent excellence (okay, that slide period aside) and mastery of every aspect of the game (except for his overhead?) - and a man who has the occasional emotional outburst, but who is also the most intelligent (brilliant, really) and articulate a player as I've ever seen - with the possible exception of the late, great Arthur Ashe. He's easily an all-time great (top 2-3 of the Open Era with room to climb) and a terrific person as well...but a very human one who does make mistakes once in a while.