DBZ - Watched most of it as a kid, still harbor mostly fond memories rooted in nostalgia.
Naruto - Never watched the anime. Stopped reading the manga after the first few chapters (somehwere around the start of the Zabuza arc, only ever skimmed it)
Bleach - Stopped reading the manga somewhere a little before Soul Society, heard stories about the horrible insipidity that Soul Society brought to the franchise, occasionally tune into the anime on Adult Swim to laugh/cry at how retarded Bleach has become + the bad production values of the anime (Even by TV anime standards).
One Piece - Only recently got into it, but it holds a strange sway over me. Started watching the anime around the Skypeia arc in the Funimation dub, became strangely hypnotized, and went back to start watching the dubbed anime as they release it on DVD. (Currently up to episode 13 as a result.)
Still reading the manga, haven't been keeping up too terribly with the latest arc because I've been busy re-reading as I co-opt my little sister with it. The farthest in I've made it so far has been Thriller Bark.
I don't know exactly why One Piece captivates me where other "big" shonen series either turn me off entirely or hold no interest for me. Aside from a couple of drag-on fights, I haven't been terribly disappointed. I can't decide whether it's Oda's zany noodle-people style, the pirate aesthetic (ninjas and Soul Reapers are played the hell out, Pirates of the Caribbean stirred my passion for pirates), or simply the fact that Luffy, unlike Naruto and Ichigo and all their friends, doesn't annoy the shit out of me, but instead reminds me of the truly manly boy-heroes of the old GAR classics like Galaxy Express 999.