GXP is probably the second best, IMO. it's the only one with a harem ending.
also warning: furries. but it's ok to fap because it's like a quintuple reversed reverse trap. you'll see what i mean.
in case you wanted to know,
TM:ryo-ohki(OVAs) > GXP > Universe > tenchi in tokyo
...and all the movies sucked.
but yeah definately watch GXP. you'll miss tenchi though.