Which athlete do you consider to be the best in the world?

Only Agassi was truly on Sampras's level, but even that is enough, especially considering that the others weren't bad either. After all, even having just one player who is practically your equal drastically reduces the number of your victories in major tournaments, especially in the Grand Slam series, by about half, and it also takes a toll on you mentally and physically. Divide Federer's victories by two, and what will remain?
Tennis is boring to watch now, but if another worthy player appeared, the records might stop being updated so quickly, and overall, it would be more interesting.