Check out:
- Barajou no Kiss
- Hakushaku to Yousei
- Kaichou wa Maid-sama!
- Kimi ni Todoke
- Ouran High School Host Club
- Shugo Chara!
- Special A
- Vampire Knight

I'll give you a few...
Gentlemen's Alliance- if you like romantic stress and plot twists
vampire knight- if you like vampiric/ forbidden love
wanted (not the movie)- it's not a series but a single book but it is super delicious anyway
Ultra Maniac- is you like akward beginnings love
Black bird- if you like demon/sometimes a little pg13/akward/confusing/angsty (brand new manga so its not out much yet.)(but very good don't get me wrong)

I usually don't read romance series, but the few that I have read were really really good (to me at least).

Absolute Boyfriend- a romance/ humor manga that was way better than I expected it to be.

Vampire Game- well... I consider it romance but I'm not sure if most would. It does have romance in it, but it also has a bunch of other elements in the plot besides romance, and it has a very sweet ending that I actually did not see coming.

Angel Diary- Very, very good if you like angels and demons in mangas. I'm reading it right now! It is a romance/ action manga, but there isn't so much action in it that it over rides the manga and makes it unenjoyable.

Fushigi Yuugi- Not the best, but it's pretty good.

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Oh, Oh! I had to come back and add Bitter Virgin! I just read it in the last few days and it is the BEST romance manga I have ever read in my life! I have to warn, it is also kinda sad. The reason Bitter Virgin is so good is because it is so real. It is very realistic and I have to tell you, while I was reading the manga, I could feel the emotions the author portrayed in me! :)

Absolute Boyfriend is actually one of my favorites it's quite sad and it has alot of love in it.

Kyou koi wo Hajimemasu is a good one and it's also one of my favorite but it's still on going it's not completed yet but other than that it's a good one.

Vampire knight is also about love and some fighting but i think it's mostly about love between 3 people.

Fruits basket The sweeteest/Funniest/Romantic manga's I think

and The anime is pretty darn Sweet.

Im pretty new to manga too so i know only one but its AWSOME! lol

TUXEDO GIN- a romantic comedy about a hot guy who turns
into a penguin and he tries to make his romance
work with a
human girl

i would sooo say my new favorite, alice 19th. it's like this big love triangle with frey and kyo. and alice is caught in the middle. not only is this a great romance, it's hilarious, yet dramatic as alice battles with her feelings and the disappearance of her sister.

Shugo chara!
Vampire Knight
Their really good :)

'Mamotte! Lollipop' is most definitely my favorite ^^ it's about this girl who dreams of having a boy that will protect her and be kind to her etc, and one day two guys fall from the sky but they're actually wizards taking a magic exam. the part of the exam is to find a pearl - which she swallowed by accident - so they vow to protect her and all that, and it's really cute because they end up all falling in love and later on in the series it's like magic love triangle stuff haha <3

Here are some really romantic mangas

kyou koi wo hajimemasu,Bitter virgin,special A,Kimi ni todoke,Yoru made matenai,Kare Kano, Kare first love,sky high, High school debut,Hana Yori Dango and Black Bird.
These are all my favs enjoy

sailor moon supers

Skip Beat, Backstage Prince, Honey Hunt, Boys over Flowers, Kare Kano, High School Debut.

Vampire Knight
Ultra Manic
Ouran host club
Kill me, Kiss me
Papolian
Phantom Dream
Monkey High
Ultra Cute
and Peach Girl
...sorry that all i could think of but i read like 20 books when i go to the libary...(i cant believe i forgot all the good ones)

~VAMPIRE KNIGHT
~OURAN HIGH SCHOOL HOST CLUB
~KAICHOU WA MAID-SAMA
~YAMATO NADESHIKO SHICHI HENGE
~SHUGO CHARA
~KYOU KOI WO HAJIMEMASU