Gokusen
Asuko March
Hana Yori Dango
Hana Kimi
Ouroboros
Hmm... my favorite Japanese dramas? I need to mention 6.. I just can't take out one because they are all just so good..

1 litre of tears
Ninkyo Helper
Ikebukoro West Gate Park
Hanazakari no Kimitachi e
Last Friends
Maou

This list includes some sad, some serious, some heartwarming and also some light and funny dramas and they are all amazing in their own way.
Nobuta wo Produce
Ryusei no Kizuna
Kaitou Tantei Yamaneko
Fuben na Benriya
Yamada Tarou Monogatari