The best romance anime:
1. Otome Wa Boku Ni Koishiteru- this fluffy romantic comedy is so cute, that it warms your heart. I liked the theme of a crossdresser in a all-girls Catholic School. Unlike those idiotic male protagonists of other harem anime, Mizuho is not annoying at all, nor does he look like an idiot. I find that Mizuho is cool, has a kind personality and possesses convincing charisma
2. Fate/Stay Night (its other genre is fantasy) but is based on a fantasy dating sim. At first I find Shiro's character annoying, but I've come to like his relationship with Saber.
3. I My Me Strawberry Eggs- I find that a girl's awkward lesbian feelings for her teacher makes for good romantic tension as well as an interesting storyline. Hibiki's lust for a 14-year-old student also adds to the romantic tension
4. Canvas 2- I like this anime in spite of that usual idiotic male protagonist, because of Elise Housen's characterization and her unique unrequited crush on him. It includes a complicated love triangle between a male teacher, a female teacher and one female student who is his half-French cousin. At the end, the protagonist, being a 22-year old Japanese man decides to end up with his 16-year old half-French cousin instead of a Japanese woman his age.
5. Chobits- an entertaining sweet romance anime that explores the complexities of a relationship between a human and an android.
6. Ai Yori Aoshi- I like it for being both romantic and funny.
7. Tsukihime- it was a good show until the last episode. I can't forgive those bastards
8. REC- this anime is pretty good with amazingly good-looking character designs. Unfrtunately the anime lasted very short
Best romance manga:
Chocolat- I liked this story about a 16-year old schoolgirl falling in love with a 28-year old gangster. The art style is clean and well-detailed. The panels flowed well, too.
Home- a manga is about a Japanese samurai and a Spanish maiden in a story that takes place in 16th century. I find this conflicted and awkward romance between Koujirou and Maria very enduring and sweet.
REC- I liked the manga better than the anime because the manga provides longer story, more fanservice and more in-depth relationship of Aka Onda and Fumihiko Matsumaru. I also liked the artwork.
Oku-sama wa Joshi Kousei - the plot premise about a 17-year old schoolgirl being married to her teacher in both anime and manga was quite well executed and the story has paced well with a good sense of drama. Besides I also find the ecchi manga artwork style to be very beautiful and crisp. And the animation/character design quality of is anime counterpart easily emulates the original manga artist's style and is thus equally gorgeous.
School of Water Business I like the concept in this manga. I find the pairing of a teacher and a student to be interesting. I also like the love triangle between a teacher, a female student and a male student.
Suki ni Natte mo Ii- it was pretty exciting and angsty soap opera romance manga
Arcana-- the romance relationship between the human detective and a spirit girl was well-written in a sweet way and full of suspense. The artwork is crisp, clean and well-drawn.
Bad Teacher, Good Darling (Ikenai Teacher, Iketeru Darling)- it is short but sweet ecchi romance manga. The story was both amusing and romantic.
Sensei- was a good romance manga. Although the art style was rather unpolished, the pace and feel for drama was neat and consistent. I also liked the relationship between Hibiki-chan and Itou-sensei. I wonder why it hadn't been animated yet?
Kodomo no Jikan- it was a very awesome and entertaining romance comedy anime. It also brings out a lot of laughs. It has such cute and feminine loli girls like Kokonoe Rin. I also liked Kaworu's crisp, sharp and well-detailed art style and her panel-to-panel flow is great as well. In addition, the fashion designs and character designs are very pleasant for me.
Strawberry and Chocolate (Ichigo and Chocolate) is a one-shot manga full of comedy, romance and angst about a girl having difficulties in a turbulent relationship with a stiff boorish novel writer.
Prime Minister- an entertaining light comedy and romance manga about the 25-year old Prime Minister of Japan proposing marriage to a 16-year old schoolgirl.
KIss- a romance manga about a 16-year old schoolgirl who was in love with her piano teacher since elementary and starts to realize her love towards him. It was a sweet, romantic and exciting romance manga.
7 KIss- a manga oneshot about a schoolgirl who blackmails her teacher with seven day kisses (one kiss per day) starts to develop feelings towards him.
Chocolate Cosmos-- I've read only three chapters but it had enough promise to be a great romance manga.
Sukinara Sukitte Ieyo-- it was a short-lived but kawaii and sweet romance manga