While I do like McCain, if I had to pick a Republican, I would like to see Colin Powell in the Oval Office.
If I were to pick a Democrat, I really like Joe Biden.
http://www.votewithavengeance.com/biden.html
He is extraordinarily bright, well versed in international affairs as well as domestic issues and he knows how to get things done in Washington.
And perhaps in 2016 or 2020 after she has finished her two terms as governor and at least one term as Senator, I think I might like to see Janet Napolitano in the White House. (Current governor of AZ
http://www.governor.state.az.us/ )