I have always admired him for having the courage of his convictions, for not caring too much what others thought about him, and most of all, for maintaining his sense of humor and optimism about himself and the world around him.
Too many conservatives, and libertarians for that matter, are seen as, and some really are!, humorless or pessimistic (see Robert Bork for example). Reagan convinced many that it was possible to be a happy, optimistic, and funny conservative. That alone was probably responsible for a tremendous shift in the perception of conservativism in the US and the rise of the current generation of baby boom conservatives. He was also a man of ideas. He was much better read than people have given him credit for, and more important, he believed in the power of ideas. That sets him apart from every president since World War II, at least. The combination of idealism and optimism and humor was also important in getting things done despite significant opposition. He was, for better or for worse, a good model of leadership.
I have often used a quote that Reagan kept on his desk, although he didn't write it: "There's no limit to what a man can do or where he can go if he doesn't mind who gets the credit." Another fine model for leadership.
Love him or hate him, he changed the world, and he'll be the last man of ideas to run for president.