I am a manga collector, and actually I don't read manga online. I buy them. So you can imagine how many volumes of manga kept in my private room (more than 3000 volumes).

I recommend:

1. Yakitate!
2. Addicted to Curry
3. He is my Master
4. D-Gray Man
5. Samurai Deeper Kyo
6. Kindaichi
7. One Piece
8. Rurouni Kenshin
9. Getbackers
10. Detective Q
11. Keroro
12. Verdant Lord
13. Gintama
14. School Rumble
15. Magister Negi magi
16. Whistle!
17. Law of Ueki
18. GTO
19. Saint Seiya

And there are more, but I only have their Mandarin titles. I dunno their english titles.
About the bad manga titles, I would say Shaman King. Becoz the ending is kind of ridiculous. After I read that ending, I realized this series has wasted my money, on buying all 33 volumes of them.

Fortunately, the anime version is much better than the manga version.

And another bad manga title IMO, is Conan The Detective. At first, it's quite interesting.  But somehow the content is kind of confusing. And the story is too long, making it started to become boring nowadays. 

i buy manga at petaling Street KL & sungai wang. mostly chinese manga.
they have few malay version too. go check it out 

kinokuniya klcc

they have japanese version too.