I don't know if they are best, but these I loved most so far:
Rurouni Kenshin
Fruits Basket
Saiyuki
Hanazakari no Kimitachi e
Love so Life
Natsume Yuujinchou
Blame! impressed me the most, a grand adventure of a single man in an giantic apocalyptic cyberpunk world with countless bizzare civilizations and societies.