Shawn Kemp went 22/14/2 on the Rockets in the 96 series vs. 18/10/2 for Hakeem, but nobody would ever say Kemp > Hakeem.
The Sonics matched up Hakeem well, and used a swarming defense and quickness to drastically reduce Hakeem's effectiveness. It's all about matchups at the end of the day.
Robinson, on the other hand, had many series where he underperformed against expectations, because there were MANY teams that matched up well with the Spurs. It was widely known the Spurs had no outside shooting, and the best way to beat them was to swarm the middle and force the perimeter players to beat you. Outside of Robinson, Elliott was the only person who can consistently create his own shot, which means that opposing teams can double/triple Robinson off of Avery Johnson, Vinny Del Negro, or Rodman. When a player is constantly doubled and tripled, he underperforms. The trick is to have your teammates make up for your loss in productivity by nailing wide open shots.
There hasn't been one single player who did not suffer from a productivity standpoint when the opposition decides to suffocate you. Even the great michael Jordan had a letdown series against the sonics in 96, but nobody cares because the bulls won.