Sampras is the king of tennis history with more grand slams than any other male player in history, but even if Federer surpasses his record, Sampras will still be the greatest because he did it against better players, for longer, and he did it quietly without the paparazzi or IMG.
Fed-heads counter that, Sampras may have more, but 1) not for long and 2) he's so much better than the competition he's doing it even better than Sampras did.
Along the way there are a few silly arguments about whether their single match in 2001 is an indicator of who was the better player, but I beg to differ. One match does not really give a basis for who was the better player. Sampr-assers will argue that Pete was not in his prime, but Fed-heads will counter that neither was Roger. Both points have merit, the only time head to head comes into play is as a tie breaker when the two players in question played in the same era, against the same pool of opponents with similar results. At that point we can start to ask how they fared against each other, but until then there are far more representative measures of superiority.
For me the most important is the number of grand slams they've won. Sampras has 14 and Federer has 12 - as far as I'm concerned the argument ends there. Of course, if Federer scores another trifecta in 2008, I can't say the debate doesn't reopen - and why shouldn't it? Years at #1 are a factor, but to me, less so than grand slams because even Marcelo Rios was ranked #1 at some point and he never won anything even remotely important. For that matter Nadal is, for me, a much better player historically, and he's never been ranked #1.
So if Federer can overhaul Sampras, I'd give him the edge.
Interestingly, the debate is almost as much about how they've gone about amassing their grand slams as how many they have. A lot of people have referred to Sampras' battles, and the pedigree of players he overcame to win his titles, like Chang, Courier, Agassi, Becker, Kafelnikov, Kuerten, etc. For me, this is a strange argument - because in a round about way it sounds a little bit like this:
Federer wins all the time, so he's the best, but it's not that impressive because he wins all the time. Implicit in this is a couple of things that call into question Federer's pedigree against that of Sampras:
- It's harder to win close matches than it is not to drop a set for 2 weeks
- It shows more character to win in the fifth, than it does to win in straight sets
This strikes me as something of a cynical argument, however, because in order for Federer to be adjudged the equal of Sampras, he'd actually have to do worse against his contemporaries than he has (thus improving their collective pedigree). So in order to be considered the greatest, he has to have lost to some of his contemporaries along the way. That sounds counter intuitive to me, and as such I cannot endorse it as a good measure of Sampras' superiority - I think Sampras' record is enough for that, and if you throw in the number of years he's been #1, and his longevity, (the time between his first and last grand slam was 12 years) a good case can be made that he's the greatest, even if Roger gets to 15 or 16 in 2008.
Another knock against the both of them is that they've never won the French. Of the two, I think Roger has the best chance because he's been in 2 finals already, and many have questioned his tactics at the French. Perhaps if he can employ a more attacking version of his game on clay, he just may find the way to break his duck at Roland Garros.
Ultimately these questions are primarily aesthetic. Whether you prefer the one or the other, it's pretty clear that objectively Sampras is the greater champion...for now.