Ah! My Goddess captures eloquently the emotions it displays in a clever story. It has a lot going for it. It is actually laugh out loud funny, the music is brilliant, and many characters smack of feeling real.
Oddly, Belldandy, the Goddess, is the least interesting of the characters. Both of her sisters. Urd and Skuld, have likable personalities, as does Url's mother and many other satelite characters. The relationship between Belldandy and Keiichi is used to introduce inventive "problems" and story plots.
It's an uplifting comedy. Both comedic and humorous, The series lacks resolution because there are going to be more seasons of this one, almost certainly.
It never hurts that the music of an anime is good. The first main theme and the second closing theme are both delights, but the incidental music in the soundtrack, too, is quite a bit better than most animes.