it's been great but it would be even greater if he won the US Open and/or finished the year at number 1
The number 1 will depend on really a few tournaments now :
there will be the period Olympics-Canada-Cinci-US Open,
and then the Basel-Bercy-WTF period,
with nearly only Shanghai in between, except that Djokovic will also play Beijing, which Roger will not play, which is an advantage in points for Djokovic.
Fed, Djokovic and Nadal are nearly equal in the Race now then the number 1 in the end of the year will be the best in these tournaments.
It will be so short, good surfaces for Roger if he's fit, and some results might depend on very few things like last year's US Open semifinal or the draw (there are more dangerous players this year than last year).
I think you've read the comments "Fed is not the best player in the world, it's still Djokovic" : what's true is that they're very tight and then it's logical that this comment is made, which shows that if Fed can stay number 1 in the end of the year, it will be even greater
Roger has said that he thinks last year's US Open could have been very different in the end and he could really have won it (I really think the same for last year, 2010 he looked less good imo), and I think he really wants to win it this year