What is grammatical?
I wish you would be more romantic
Or
I wish you were more romantic
Why?
What is grammatical?
I wish you would be more romantic
Or
I wish you were more romantic
Why?
Both are fine grammatically, but I think there is at slight difference in meaning.
"I wish you were more romantic" means "I wish you were more romantic in your nature, because then you would always buy flowers for my birthday"
"I wish you would be more romantic" means "I wish you would remember that you are supposed to do romantic things like buying flowers for my birthday"
One wish is about who you are, the other is about how you behave.