Lol I like tennis and all but it does not have a "playoff" system. There's multiple equally important majors throughout the year, like golf. Too many different possible champions every year to be in the running for best playoffs. There can only be one.
NBA is so LOL in the first round(s) every year so that's out, even though the Finals and conference finals can be awesome.
NFL has exciting playoffs in general but I agree with those above who say the Superbowl is, as a rule, lackluster (NFC/
AFC 'ships are the best).
Serious question: is the World Cup a "professional" playoff? I didn't think there was a salary for national teams (a la the olympics). Don't know enough about Premier League or other professional soccer playoffs to comment (bores me to tears).
I think it's gotta be down to Hockey and Baseball for pro sports (if we're talking overall playoff quality), and from there I side with the fall classic of baseball. Mostly because they have the sense to shorten the opening rounds, so we can get to the good stuff of the WS while also giving wildcards/cinderellas/hot hands a more realistic shot at advancing or at least shaking things up (unlike 7 games for every damn round in hockey - takes half a year to trudge through, and megacorp teams just outlast newcomers {this is my Blues fan colors showing - damn Hawks

}).
Hockey has the slim edge in terms of "taking things up a notch" more than any other pro sport. Those guys straight up battle and sacrifice the body. Baseball does too but without the pure physicality. NFL, if anything, drops off pretty often. For whatever reason the regular season rivalry games and the earlier playoff games usually outclass the Superbowl in intensity. (The NBA majorly ups the ante - technically more than the others- for playoffs, but they are disqualified because that's a relative measure to their anemic, if not pathetic, regular season play).
Rant over.