I've really been having a hard time with this one -- I keep starting to reply and then going away because I can't just settle on one. :
Try to remember what manga got you really anxious for the next chapter or made you read till 4 am even though you had to wake up at 6 am that same day.
If this is the criteria, then it's a bit easier, but I still can't narrow it down. So I'm going to cheat and give you more than one answer, rather than going away AGAIN!
The best manga ever for me is Naruto -- and One Piece is either tied or in such a close second place that it's no difference whatsoever. These two are the ones I can't wait to read, and the ones that kept me up all night when I first discovered them and read to catch up.
The best raw manga I've followed voraciously and wished 3 times daily that someone would scanalate on a consistent basis is MAJOR -- particularly now that the anime has ended before animating all the chapters of the manga! This manga is the one that is responsible for me deciding to teach myself Japanese so I could read it for myself, I'm that desperate!
