Fist, I must say I'm not a fanatic of the cinema. Simply, if a film is truly good, I like it.
But if I have to choose... I don't choose science fiction or adventure films. There are a lot of people that say these films are exciting and funny but I don't think so, I don't like them. Some of these films are too fantastic.
About horror films; I like them, especially when I go to the cinema with my friends. but sometimes, these films are really scary!
Then, I don't like comedy films. A lot of comedy films aren't funny, on the contrary!! You can guess the end of most of these films without seeing it.
I supose romantic films are the best... My two favorite films are romantic films! They are "If Only" and "The Notebook".
'The Notebook' is about one boy and one girl, and all the story of them is the diary of the boy.
And 'If Only' is a film about one boy and a girl too. In this film you must think a lot to understand it from the beginning... but it's a lovely film! It's the only film that makes me cry when I watch it.
So, finally, I think romantic films are the best, because love is the best thing in the world.
Here is a video of If Only;
And here one of The Notebook;
This films are the best I ever watch!
see u!

Is "if only" a film about a girl who dies in a car crash and then her boyfriend is given a second chance ? As for the other film you talk about, is it an American film, a Spanish film ...? I can't find it on the net under the name "The Diary"