I've preferred dark animes like Elfen Lied and Higurashi since the beginning, and the latter made me a huge fan of murder mysteries with horror elements. However, I like to balance my anime diet with harems in the mix, so my brain can have a break from all the mindfucks.
Definitely Romance is the best, but maybe Sci- Fi, or comedy would also be a good genre.
From the Mangas that I've read so far, I think there is a overwhelming amount of romance manga.
To make the master dish you must add a slice of ecchi add in some comedy also with a teaspoon of action don't forget a litre of romance a cup of drama and spoon of fantasy serve with anime enjoy!
Romance, comedy and horror are my absolute favorite but if I had to choose I'd choose romance. Sometimes they just seem to spice up the anime very well.