Again, if we're ranking these players based on raw output and talent, then obviously Gervin is better than Tony and Manu. There's no discussion there.
But my point (and I suspect others') is that since we're ranking them according to their importance for the Spurs franchise, then things get muddled a bit. Gervin made the Spurs relevant after the merger, and probably contribued to the franchise staying in SA. But Tony and Manu are part of the winningest trio in the NBA, at a level of sustained excellence never seen in any American pro sport, also main contributors to 4 championships, and are not in any way, shape or form role players.
That's why I'd give them the nod as 3a/3b in terms of All-Time Spurs, even though they are not individually as good as Ice.