Detective Conan forgot it had a plot though. That's a problem. 
If you haven't watched One Piece I suggest you do. It has a refreshingly unique style, great orchestrated music, lots of great comedy, and decent action without the WAY overused anime DEM. The only problem with it is it's plot is obviously cyclical and follows it's own formula pretty much the entire time. It's gotten better about bending this in recent arcs though.
Detective Conan is just plain fun, but like I said it really needs to do a better job of remembering that there was once a plotline there. Other than that it's great. Did you ever watched Hayate no Gotoku? That's a great unique, funny, anime too.
I do find that I like some mainstream (if by mainstream you mean released in America) animes, but usually only in subtitle form. Still, you said you don't like mainstream anime, but your #1 pick on the anime topic is Zoids: Chaotic Century which is about as mainstream as they can get. It ran on Cartoon Network for years and sold lots of toys. I agree it was good, but again better as a sub.
I watch an odd variety of animes. Currently I've been watching Noir, which was obviously written by someone on acid, and Hayate no Gotoku, which is just awesome. I'm hoping the new Gundam 00 gets the taste of crap out of my mouth that Seed and Seed Destiny left in there too.
