The NBA and NHL have fairly similar structures to them. Each league plays the same number of games, 82, plays the same length playoff series, 7 games, and lets the same number of teams in to the playoffs, two 8 team conference playoffs. Both have a problem with their playoff structure from my point of view. However, it is not the same problem for each. In the NBA you have a number of teams that have little or no chance of winning even after making the playoffs. The talk-show hosts in Chicago discussed whether it would be better for the Bulls to make the playoffs or miss and improve their draft position. Getting the 8th seed has very little value in actually winning a championship. In the NHL since every team can win the regular season matters very little if you are in playoff qualifying position.
This year the semi-final matchups in the NBA will feature the 1 and 3 seeds facing off in one conference and the 2 and 4 seeds in the other conference. The NHL will also not have any duplicate seeds between the conferences as the 1 and 2 and either the 6 and 8 seeds or the 7 and 8 seeds.
This outcome in the NHL vs. the NBA is not new. Since going to approximately the current playoff system the NBA has seen three 8-seeds beat 1-seeds in the first round in 54 matchups. These results may overstate the likelihood of an upset as two of the 8-seeds won 5-game playoff series, rather than the current 7-game series, which should give the weaker team a better chance. Also one of those two seasons was strike-shortened, so the regular-season performance should be less tied to post-season performance than in a normal-length season. In the NHL, 8-seeds have beaten 1-seeds nine times in 32 matchups. Only one of those came in a strike-shortened season and all of them were in 7-game series.
Here's the thing. Neither situation is optimal. The NBA situation simply adds in teams with no chance of actually winning, while the NHL situation leads to a de-valuing of the regular season as any team that makes the playoffs has about as good a chance of winning. The difference in outcome is probably attributable to differences in the nature of the sports (less competitive balance in general in the NBA, hot goalies in the NHL). Regardless of the cause the problem is too many teams in the playoffs and it does not depend on the underlying nature of the sport.