IF you want to watch a long running shonen series without alot of filler then watch one piece . Because out of the 301 one piece episode that has been released so far, roughly about 55 is filler. Bleach has 55 filler out of the 119 episode, i don't even need to give you the numbers of fillers for naruto.

One piece is your typical shonen type story, except there is alot of original twist and the art is quite different compare to the typical shonen drawing style. So you should try it out if you're into action/adventure mixed with wacky comedy.