For example (since the banner for this site has changed has triggered my memory) - bleach. I've watched all of about half an episode of it and for the life of me it didn't catch me at all. Yes, it was some sort of 'filler episode' where the main character was in the hospital for some-such reason, but just watching the episode and reading the dialong (as I believe it was a fansub a friend was watching), it just didn't have 'it' for me at all. I guess it didn't intrigue me at all.
Naruto - watched an episode of this on CN a while back as this was so fricken popular at the time, nearly everyone at my local anime convention was wearing a ninja headband, so I figured there must be something to it. Well, if there was, I didn't find in in the one episode I watched. All I can remember of the episode was a lot of jumping thru trees (which seems to be common, so I doubt anyone could tell me which one I was watching) and some sort of 'trial by fire' going on as well for the female lead (don't remember her name). Although I liked parts of it, I just couldn't find myself caring what happened to the characters to continue watching. Sort of like how many didn't / can't like Eva because Shinji is just a little whiny bastard (but, I do like Eva, but don't want to open old wounds

Kenshin and Champloo I couldn't get into I think mostly because I didn't, and probably still don't like period pieces... I don't now why, maybe it's just my own predudices.
Can't think of another one that I don't like yet, but I'm sure I could think of a few more, given time
