I second to:
Full House ( and add here Full House Take 2) - famous guy and average girl
Skip Beat ! - famous guy and average girl, adaption of manga, drama covers only some first story arcs, so if you like drama you can read story til end from manga.
Last Scandal - famous actor and average divorsed house wife, like you see characters are littlebit older but story is good and funny.
I would add:
Mukodono! and Mukodono 2003 - famous star and average girl, guy has two very different faces - one for professional life one for personal life.