I think my favorite anime's Macross Plus. It's not exactly long, but it is great. Terrific voice acting (english.. I haven't heared the japanese voices), good animation, and a very good plot..
Second, though, is Tenchi Muyo (The OVA.. I hate the way they overditzed Mihoshi in the tv series..), but maybe that's just because it was practically the first anime I saw and really liked off the bat. (Saw DBZ first.. after a while I think it gets boring, though..)
EDIT! --I'm talking about the Japanese subtitled version of DBZ. I forgot when but I encountered it on the international channel. The first block of dubbed DBZ episodes (up until about the point cpt. Ginyu switched bodies) The voice acting was good.. but after that it was like they yanked a bunch of twits off the street and told them to talk like pro wrestlers. I half expected the line "That's the bottom line, 'cause Vegeta sed so!!!" to pop up.