 If you liked
Aa! Megami-sama!
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 ...then you might like
Tenchi Muyou! Ryououki
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Both shows are 90's harems, but Aa! Megumi-sama is a little more subtle about what it's trying to be. While Tenchi is more upfront and obvious about being a harem, Megumi-sama's main character by the end of episode one is already in a relationship. This goes against Tenchi's "Anyone could hook up with Tenchi and it's completely up in the air."
Both shows have multiple women living under the same roof with a young man, and the girls are associated with aliens or have some kind of supernatural abilities.