The most important part that is overlooked here ALL THE TIME is this:
Between 1993 and 1998 - ALL of Sampras' year-end-no-1 seasons, he only faced Agassi a total of 3 times in the majors.
Three. freaking. Times. Once at Wimbledon in 1993 when Agassi played with a broken wrist and pushed Sampras to a 5th set. Once when he beat him at the AO in 1995. And once when Agassi was drained after his SF win against Becker in the US that year. That's it. 3 times. For comparison - Federer faced Nadal 3 times in majors in 2005-2006 and that was just the beginning of their major meetings.
The reality is - the only reason Sampras "main rival" Agassi looks actually like a main rival is because he racked up slams in his 30's when Sampras was past it. Imagine if Agassi went down on himself and retired in 1997 or 1998 after some humiliating losses and his ranking falling to 127 or something. The next in line after Sampras who won the most majors in the 90's would be a guy who won a total of 3 majors which is laughable. Now, while Federer is at 17, Nadal is at 11 (Nadal is VERY MUCH a part of Federer's generation - he's been there since 2005), Djokovic at 6 and Murray is surely going to win a couple.
Just shows you how pointless H2H's are. Nadal beat Fed but in the end it meant jack, they both walked away with nothing. It's about winning titles.