This is what I'd say:
1. One Piece (By far the best of the 5. Amazing character development, enjoyable action, and has stayed entertaining while remaining the longest. Probably the only arc I can say I didn't care for was Fishman Island, the rest was fantastic. OP has what I would deem to be some of the best Shounen backstories ever created, and even if the main plot isn't really "strong" or "deep," it's very entertaining and the adventure element keeps the series fresh throughout.)
2. Fairy Tail (Not as awesome as One Piece but still very enjoyable. Admittedly it has some Deus Ex Machinas and some characters don't seem to progress as much as they should, but it's still very entertaining. Great fights, enjoyable character development, and just a lot of fun overall. In particular I liked Erza's arc best for her character development and for the way everything played out).
3. Naruto (A mixed bag. At its best it's definitely entertaining and is just as good as the other two. However, at its worst it's filled with Sasuke melodrama and a lot of Deus Ex Machina that's obviously there to cater for the Sasuke fans, whom I still cannot understand. Sasuke has proven himself to be an awful character and really drags the series down, but at least part 1 was great and even part 2 had some epic moments. Kisame in the later stages of part 2, the backstory with Minato and Kushina, the story of Hashirama and Madara, and probably others I'm forgetting were actually pretty awesome).
4/5. Dragon Ball Z (Good for action and nothing more really. The plot is way too simple, the character development is pretty minimal, and honestly there isn't really much depth to it. Truth be told, part 1 Dragon Ball is much more entertaining due to the martial arts element and the sense of adventure, while DBZ is just a lot of guys throwing energy blasts at each other and little else. It looks cool, and that's about it.)
4/5. Bleach (Honestly I'm not sure if I'd deem this above or below DBZ. For a while I would definitely have put it below because everything after Soul Society arc was just god awful plotwise and characterwise. Not to mention awful plot twists that weren't used right and Fullbring arc being absolutely pointless. Bleach definitely takes the cake for some of the worst moments in a Shounen action manga. However, Soul Society arc was still fantastic and the newest arc seems promising and, for the first time in a while for Bleach, is actually entertaining. Truth be told, The Thousand Year Blood War arc alone is much better than anything in DBZ. However, Bleach is still bogged down by a very terrible middle, so while I'm iffy about putting it below DBZ, I'm not so sure about putting it above either.)