The one thing that, I think, we can be totally certain of is that neither Larry or Sergey are business geniuses. I can't actually think of more inept business leaders...even in that rarefied category of utter incompetence that is the dual share class crew, they look pretty bad (worse than Zuck even).
Page, in particular, seems to have a real talent for finding creative ways to light big piles of cash (other people's obv) on fire.
Yes, Brin seems genuinely intelligent and the work he, presumably, did on Pagerank obviously had tremendous business value. Everything that I have read about Page suggests that the only distinct idea he has ever had is that he is a genius (the story about the monorail at Michigan struck me as the grandiose, self-important delusions of a privileged infant...that he tried to do this as an adult, and then again when he was in his thirties is...just sad).