For someone living outside of America, David Robinson was the reason i became a Spurs Fan, and to me will always be the most popular.
However, it is all probably based on when you became a Spurs fan, or a fan in general. For people joining now, David Robinson would merely be a 'Huh, whos that?' - TD, TP and Manu would be the most popular. In 50 years time, it will most likely be someone else who is the most popular. Ice, DRob, TD, TP, Manu will probably be forgotten for this 'new stud player'... a case of 'what have you done for me lately'.
So, sure - now Manu might be the most popular (which is probably fine with Timmy, less focus on him) - but down the line... will he? Probably not.