The highest pursuit is the search for truth. This includes the challenging act of discarding things that we'd really like to be true, but are false. The success of science can be attributed to extreme selfless intellectual honesty. The more ego gets in the way, the more the truth is compromised. Intelligence can be used in service of finding truth or in feeding our delusions. My view on the distinctions made here between genius and madness are that they correspond to the degree in which intelligence serves truth or delusions. Therefore I'd expect the most outstanding scientists in history were also very humble (perhaps someone with better knowledge on the personality of great scientists can shed more light on this).
And to keep things consistent - I might be wrong and thus welcome challenges to this theory :)