In politics, timing is everything. Obama was drafted more than anything else because many wanted him to run. As we may recall, Hillary opted to get more Senate experience and declined to run in 2004. And also one should remember, anyone running from the Senate does not want their senate re-election date to be a one out three Presidential election year.
And besides, its character and not experience, IMHO, that defines a persons ability to be an effective President. That and the judgment to choose good advisers that have decades of experience and expertise in a wide variety of areas.
Sadly, McCain and Ron Paul, while they have some qualities the times call for, got the short end of the stick when it came to timing. The times choose Obama and Obama must play the cards he was dealt.