
1. Rurouni Kenshin (both the anime and manga are excellent

2. Ouran High School Host Club (both manga and anime are hilarious, but the anime doesn't cover the whole story)
3. Honey & Clover (2 seasons - really good if you like slice of life, comedy stuff)
4. Saiyuki (haven't tried the manga but the anime is AWESOME)
5. Detective Conan (i love the manga but if I have to compare with other series I've read/watched then it does fall a bit in ranking...)
6. Kimi Ni Todoke (manga - just started reading, very funny xD)
7. Doraemon (classic!)
8. Tsubasa Reservoir Chronicles
9. Yakitate! Japan (SO FUNNY)
10. Meitantei Loki
very hard to list! but the top 5, at least, will be permanent favourites i think.
EDIT: oh crap I forgot about Nodame Cantabile. I knew I would miss out something :/ well I'll just pretend I can insert a 5a there. *whistles*