Fairy Tail, the first Manga that made me read all 140 chapters in 2 days.
(I was originally just going to read a chapter or two to see what it was about...)
I really do hope the anime doesn't turn out shit, the last thing I want is an adaptation ruining the manga reputation.
For me though:
One Piece - All the crap it has + Awesomeness + Even more Awesomeness = Fairy Tail
Though, having said that, I wouldn't want to compare them too much. The artwork reminded me of one piece, but one piece had grossly overdone crying and often character facial expressions failed.
^ I Friggin' lol'ed. Will never forget that scene XD