Kimi ni Todoke
Ore Monogatari
Clannad
Say I love you
Inuyasha
Nana
Toradora!
You can find great suggestions here:
https://myanimelist.net/featured/1533/Top_25_Best_Romance_Anime_of_All_Time
https://www.anime-planet.com/anime/tags/romance
http://onlinefanatic.com/top-10-best-romance-anime-good-recommendations/
http://www.animeranker.com/anime/best-romance-anime/