I like all of them, although im gonna say I like One piece out of the 3. Naruto started out alright, but got bogged down by annoying characters and too many filler episodes(even if some of the filler arcs ater tied into the main story). It seems like its starting to get better (in the manga anyways) but im holding my breath, it seems to have a pattern with this.
Bleach started out really good too, it seemed a bit fresh, and while not completely reinventing the "anime about guy with superpowers", it did do a few things right, up until it had more in common with DBZ than the anime's it should have been compared to (yyh and the like)-_-; and the story began to get pretty convoluted, and pretty much barely even explaining some characters motives at all, too much, or not soon enough (ichimaru for that).
As for why I like one piece, there are quite a few things to mention. The characters, major or minor, all seem to be interesting, both in design and in personality. It does quite a few interesting things with the "people with superpowers" concept (see eva for this one, seriously). All the main characters seem to be likable and their antics are fun to watch(good thing =P). The show, while light hearted quite a lot of the time, can actually be pretty dark and depressing (see the mary go, the enies lobby arc, and the most recent whitebeard vs navy arc).
I could say more but I have rambled for far too long. For those who are on the fence about watching it, give it a shot, just dont watch the 4kids dub version of the show(its the most well known version for non fans, and the reason why many people were turned off of the show), it basicly defiles the show.