Last year, if you take the entire season into account, he was FAR and away the best player. Nadal was injured, but that isn't his fault. He made all 4 slam finals, which nobody else even came close to doing. And by winning 2 slams, he blew everyone else away in terms of results.
Roger is nearly 29, so he has some years left in his legs, but he is going to get old. That's just life.
IMO, Roger is a victim of his own success. People hate him because he has been so good over the last 6 or 7 years, but it had to eventually start to tail off. I think he realistically needs to lower his standards a bit, as do his fans and doubters. Obviously he wasn't going to continue winning 2 or 3 slams every year forever. Eventually he had to reach a point where his level of play and his body were going to restrict such incredible results. Today, he rationalized his results in both Paris and London, saying it is "still the Quarter Finals. People would die to play in the QF of a slam." I think he is beginning to, based on his life and the way he has been playing since January, to understand that he just isn't going to be in every final, or for that matter every semi final. It's sad to start to think about that, but he has already accomplished so much. If he can get all of his health in order and work out the mechanics of his game, he can recover to a good enough form to win a few more slams, compete at the 2012 Olympics and recover the #1 ranking and break Sampras' number of weeks record. But time will tell. Next year, he'll have a lot of points to make up and very few to defend after the AO, so if he can work things out, he will likely have a good chance to do all of those things.
(Lol at the above, Roddick is the future? He's 28. -_-)