Sprot that get playoffs right:
NFL - 12 teams out of 32 in the playoffs. The top 4 get a bye to the quarterfinals, home field really does help (unless you live in Kansas City). Only 16 games. The regular season matters. So naturally the NFL has been pushing an expanded playoff
Sprots that kinda do playoffs right
Baseball needs a 3 game series for the Wild card, but at least the absurdly long regular season matters only 8 out of 30 get in.
Not great
MLS - 12 teams in (too many) but 8-12 have to play an extra round. However the playoffs have been crap since they installed the away goals rule.
Bad
Hockey - 16 out of 31 teams in (better it used to be 16 out of 24 teams), seedings don't matter, a 7-8 seed can win the stanley cup. The regular season is way too long and pointless.
Basketball - regular season basketball is no different than a glorified friendly, repeated 82 times. The bottom 8 teams actually try to lose to get better draft picks. You spend 9 months waiting for that 1-2 collossal 7 game series matchup and by the time late May hits those matchups suck because one team is usually riddled with injuries (the upcoming Houston-Golden state match is an anomaly). Hockey playoffs have way too many upsets, basketball is the complete opposite. You already know who's going win.
The only time regular season hockey and basketball is good is when there is a lockout/strike and 1/2 the season is shortened.
Controversial
College football - I enjoy it but I'm not going to explain it to you brits becuase you don't care anyway.