It's like... Tenchi Muyo, Love Hina, Negima!, Ah! My Goddess... basically, the central character is a guy and has 4+ girls (usually quite sexy ones) interested in him/hanging around him.
The only one I really enjoyed was Tenchi Muyo, mostly 'cause it was hilarious and sci-fi.
Meh, I saw much of the anime of DBZ, and played some of the plot based games, so I don't wanna go read it when I have already seen it, and maybe I'll do One Piece some time, but not now. :\