I'd say thats about right. Shaq came in to the Magic as the team savior. he and LeBron have really been the key part to their team's success over those years. The Spurs on the other hand were already stacked with Elliott, D-Rob, and some really good players around Duncan. Plus Shaq and LeBron have put up better numbers than Timmy. Remember, the Spurs were really close to the NBA finals before D-Rob got hurt and missed the entire season.
This does not mean I think LeBron or Shaq are better than Tim, especially Shaq, but I do think as number one picks Shaq and LeBron were more better for that team.