How is this even a question? Of course DBZ is the strongest universe. I have no doubt that Gohan/Goku/Vegeta would take a steaming dump on anyone in the One Piece/Bleach universes considering how they're all just a bunch of one trick ponies (devil fruits/bankais etc) and have very little diversity in their skillsets. A case could be made for Naruto that Izanagi users could beat someone like Krillin by surprise (die, then reanimate and kill), but even then, they'd be crippling themselves for life to pull it off. Guys like Whitebeard and Yamamoto would have trouble fighting Tien.
I hope by 3 you mean Naruto, Bleach, and DBZ because no way in fuck does YYH beat OP as a manga.
YYH art is crap (and by crap I mean CRAP). YYH has pretty good characters (kind of bland though) and a good story line (pretty one-dimensional though). It lacks the complexity, scale, and foresight One Piece has. Not to mention lacking any sense of humor. YYH is a good manga, definitely beating out Naruto and Bleach, but no way in fuck does it match One Piece.
Personally, I'd prefer DBZ > YYH. Just because YYH's art is SO BAD. It's hard-for-me-to-read-this-bad.
Could be worse though... could be Hunter x Hunter where he has chapters that were actually published as rough draft sketches. wtf
Okay, I know that Naruto is a shell of it's former self, but no way it belongs in the same category as crap like Bleach, DBZ, and Fairy Tail. These stories have no substance whatsoever and are just a messy agglomeration of fights (although DBZ can be excused as it's the first manga that pulls this off). And lets be honest, you know how the fights are going to go before they even start. Bleach usually goes something like: random captains/vice captains beat the henchmen, then the arc boss shows up and Ichigo comes in and bs haxes his way to victory. DBZ usually goes like: characters train/get power boosts, fight on even terms with the villain, villain reveals a powerup and starts stomping, Goku/Gohan deus ex their way to victory. Words cannot even begin to describe the joke that is Fairy Fail. Up until the Pein arc, fights in Naruto were unpredictable and the winner was often decided by who was the better strategist, not who had more hax jutsus. At one point, the story had significant depth and complexity (albeit not to the same extent as One Piece), it left you wondering about the unrevealed secrets (again not as consistently well done as One Piece), and no manga has remotely close to as many emotionally moving scenes (and no, things like Robin's backstory, Wiper's Light of Cyandora scene, or Ace's death scene don't even come close to Sasori's backstory, the confrontation at the Valley of the End, or any of Naruto's death scenes). I'd even go as far as arguing Naruto at it's very best is better than One Piece (OP>Naruto overall though due to the latter's inconsistency), and at the very least Naruto>>>>>>>>Bleach/DBZ/Fairy Tail.
Overrated krillin is overrated, 3 arcs ago i wouldve said he solo'd anyone in naruto cuz he Lolz at OP or bleach power levels (tho i know barely anything from the latter), but then naruto dodged the fastest guy in earth's punch and madara pulled a meteor from sky.
But i agree with chou, higher power levels =\= great manga, i personally find naruto and OP really good, fairytail used to be good as well, but yea not anymore. So how do you guys qualify a manga as good?
Umm you sure we're reading the same manga? Fairy Tail has literally been the exact same thing since D1.
IMO, the most important criteria are:
-how likeable and deep are the characters (Naruto is amazing at showing the inner clockwork of every character, Fairy Tail is horrifyingly terrible)
-how well the story is paced and how well everything is tied in (One Piece is otherworldly at keeping everything in line, Kateyo Hitman Reborn has no direction whatsoever)
-how the conflict is built up, maintained, and resolved, doesn't necessarily have to be a fight (Fullmetal Alchemist is non-stop action and suspense, DBZ is guaranteed to be resolved by deus ex machina)
-how much it makes you think and how are big reveals are handled (Death Note makes your jaw drop because you don't see half the stuff coming, Bleach makes your jaw drop because it's blatantly obvious complete asspull)
-the most telling characteristic is if you start at chapter 1, how motivated are you to continue reading (Death Note/FMA make you almost want to read every chapter in 1 sitting, Fairy Tail makes you want to break your laptop)