FOR YEARS in the latter part of his eventful life, Marion S. Barry was something of a figure of fun, at least to many people who didn’t live in the District of Columbia. He never lost a passionate constituency of admirers in this city. But for many, it became all too easy to forget, as this city’s four-term mayor went from one crisis or scandal to another over his long career, that there was a time when he was a widely admired leader in his adopted home town.