Best for me or greatest overall?There a difference you know!
Best for me?Midori No Hibi!Its smart(well...sort of)funny,romantic,and totally bizzare.Its like Love Hina on GOOD acid(with less fanservice and a chick connected to the protaganists hand)For me,nothing can even compare!
Best overall.Angel Sanctuary.Its perfect for anytone as long as they are mature enough to grasp it.Its got a good blend of genere that makes it desireable to both a male and female audiance,the story and characters are deep and complex,and the art it breathtaking.