How can you define what the best movie is?
Like I said at the end of my first post...
There is no "best" film. No film can be ranked. No form of art can be ranked.
Ranking films is purely opinion. Like you said, there are films you GF loves and you hate. No form of art is superior to another, no matter how many people say one is better. There is no point in trying to decide a best film. There will always be someone who disagrees.... and they are not wrong, because it is all opinion.
But I can't deny that it's fun to discuss opinions on film with others