I like both the anime and manga though I definitely prefer the manga over the anime.
The anime was fun, but lacked the narrative cohesion of the manga. The characters developed more naturally in the manga, whereas the anime was a bit more disjointed. I also liked the fact that the manga was able to more fully explore the secondary characters and give them more depth, especially motoko, as well as giving the keitaro/naru relationship a more natural development. I also got a bit worn out at how the anime kept stretching and stretching the Naru/Ketairo thing and never really gave it a full resolution like the manga. Granted, the manga stretched it out a long time too, but at least it gave it a real conclusion.
Still, the anime is pretty hilarious and I found it entertaining.
As far as favorite characters, from character design I'd say Kanako, as for character probably motoko.