His qualifications go far beyond 6 years in the Illinois Senate and 4 years in the US Senate - and way beyond Sarah Palin's. Arguably at least equal to and maybe beyond John McCain's, by virtue of his background in Constitutional Law plus his executive experience as a community organizer. (McCain has military experience but no formal education in law and perhaps no executive or governmental experience except as a member of Congress.)
At any rate, Obama's resume clearly shows him to be as qualified for the Presidency as many of our former Presidents, including some very successful ones, have been.