Have to say 2001-2004 as well. Andre past his peak, No.1 rankings were always up for grabs (much like WTA lol). And no one was dominating, besides Ferrero, Coria, Hewitt, Agassi which were never dominant unlike the Fedal era that we have now.
I thought 2003 was a wonderful year for tennis, despite the lack of a clear dominating figure. There were some glorious moments for past/future legends, as well as great appearances by some underdogs. The Australian Open was notable for Agassi's last major title (which helped him reach No. 1 during the year) -- but the true entertainment value came largely from Younes El Aynaoui, who played a great match to defeat Hewitt and then an epic classic against Roddick (the American prevailed 21-19 in the fifth).
Felix Mantilla scored an impressive victory in Rome.
At the French there was a second chance for Ferrero, who had squandered his chances at the title the year before. And Verkerk's run to the final out of nowhere was bizarre but entertaining.
At Wimbledon Federer finally put his game together -- his form in the victory over Roddick in the semifinals made the commentators swoon. And Philippoussis made his way past Agassi in a dramatic 5 setter all the way to the final.
The summer hardcourt season belonged to Roddick, and for a very brief period there the idea of a budding Roddick-Federer rivalry actually seemed plausible. (Unfortunately for Roddick, the Montreal third-set win was to be his last against Federer for a very long time!)
The US Open struggled with weather issues, but it still provided some great matches, including Roddick's comeback victory over Nalbandian, saving match points in the semis. I disagree with those who say that this title was handed to Roddick, or robbed from Nalbandian... but that topic has been discussed amply elsewhere.
In the Masters Series Agassi and Federer put on an amazing and dramatic round robin match. Agassi followed this with tight victories against Ferrero and Nalbandian. And then in the final Roger turned up in incredible, jaw-dropping form -- this was really the start of his years of domination.
Well, I didn't mean to write that much about 2003, but I had fun thinking back to it.