Re: Unpopular Opinions
Sampras > Federer
Sampras > Nadal
Reason being: He was head & shoulders above the rest of the competition in his era. You can't compare Slam counts because he played in an era of specialists who could clown the best all-around players at Roland Garros. However, he and he alone dominated in an era that naturally featured a lot more variety than the current semi-homogenized courts. Can't put Nadal and Federer ahead if it isn't even clear which one of the two is the best in his own era.
That said, unpopular opinion number two...
I actually prefer the semi-homogenized courts. The best overall players should be favored over one-dimensional specialists, not the other way around. It used to be that Pete Sampras would get clowned at ever single FO, while the super-slow clay was overrun by a bunch of specialists. Props to Guga, Agassi, Wilander and Lendl for saving tennis, but the best player in the world for six years barely had a chance. This way is much better. There's still some difference in the courts, otherwise Nadal would have like 30 Slams.
Juan Martin Del Potro belongs in the ITF Hall of Fame. If you don't put him in, then who do you induct from this era? The Big Four, and maybe the Bryans? Again, this comes back to the dominance of the big guys post-2005, thereby there are fewer and fewer players who breakthrough to get one single Slam. So he belongs (unless the ITF decides to unilaterally stiffen their criteria).