Lerner & Loewe have some great ones: Eliza and Guenevere for women, Higgins and Arthur for men. And there are some good roles in "Gigi," too. Especially among the supporting cast. (I think I'd rather play one of the older characters in "Gigi" than one of the younger ones. The older ones seem to have the most fun. )
well going by the Tony Awards, the most nominated/winning roles for women are :
Mama Rose - Gypsy Anna Leonowens - The King and I Desiree Armfeldt - A Little Night Music Peter Pan - Peter Pan Charity Hope Valentine - Sweet Charity Phyllis Rogers Stone - Follies Mrs. Lovett - Sweeney Todd Louise - Gypsy Marge MacDougall - Promises, Promises The Old Lady - Candide Fraulein Schneider - Cabaret Sarah Brown - Guys and Dolls Maria - West Side Story