Personal history time: Aside from a handful of Pokemon comics, Oh My Goddess was the first manga I ever read. There's no telling if it was this series in particular that inspired me to fall in love with Japanese comics, but it certainly didn't hurt.
Oh My Goddess follows Keiichi, a down-on-his-luck college kid, who one day accidentally calls the Goddess Technical Help Line. They send a goddess named Belldandy, who informs Keiichi that she can grant any wish he wants. Suspecting his friends are pulling a prank, he says he wishes for Belldandy to stay with him forever. He soon learns that it's not a prank - Belldandy really is a goddess, and now the universe will do anything it can to keep them together!
Oh My Goddess is the longest-running manga in America, published here continuously from 1994 to today. It's no wonder why it's been a hit for so long: Kosuke Fujishima's art is beautiful (though the first few chapters definitely show their age) and the plot grows right along with the characters, weaving a technological take on Norse mythology in with the romantic comedy mishaps.
Being a romantic comedy originally aimed at men, there is the occasional focus on chests (or backs, or legs, or . . .) but these are always drawn with care - more classic pin-up than modern sleaze mag.