Although I know few facts about Ms. Rice's personal politics, it would be reasonable to assume that anyone with her level of experience in government with a conservative administration, her magnificent level of intelligence and fortitude, and her lack of an amoral personality (a la both Klintons) would be excellent Presidential material. Plus Bush like her and I respect George Bush's judgement any day!
Sure there are many who could be presidential material, but would Dr Walter Williams run and win? Just because there may always be someone equal or better doesn't disqualify her ability.
Being an elected official would add no more relevant experience (except maybe how to lie in a campaign) than she already has in her federal post.
"her level of experience in government" - You think two years as a Presidential advisor is adequate Presidential training, I do not.