NHL and NBA playoffs should be best of 1.
The only professional sport that should have a "best of" playoff series is baseball, and that's only because of starting pitchers. If you're fielding the same team each game, then you should play knowing you won or go home.
Don't give me this excuse of trying to let the best team win if they drop a game for whatever reason. Champions win when they have to, regardless if you think the wrong team advanced and the better team just had a bad night.
Plus single games make it more exciting and can't miss. Just look at the NFL the Super Bowl is only 1 night and it's become a cultural phenomenon. The NBA and NHL finals, and even the World Series, casual fans can miss the first 2 or 3 games and not care at all, then pick it up when the championship is on the line.
This especially goes for hockey which has no business being played in late spring, early summer. It should be ending playoffs in April, not just starting them for 2+ months!