Dave,
Do believe that you are right on the money with the Top 3 Prestigious Races. I dont believe the Worlds would be in there as they are held in different locations each year and from what I have seen and heard from most riders they put more importance on the classics. Then there are always the Olympics. But there again it is a one shot race. We could always ask Lance and find out his feelings on the subject. Frame builders always love to have the World's colors or Olympic rings on their frames though.
Regards,
Mark P. Sunny and cool here in the mountains of WV