if you define nice as acting in a way that is correct according to social or moral rules.
It is probably not enough because most women have multiple suitors and if all you are is nice then that is not enough to cause a woman to fall in love with you.
Almost all of the woman I have got said that I made them feel special? What did I do? I was overly complimentative and flirty. Did that come off as nice to them? Yes.
But that's a different kind of nice. It is a nice in a romantic way. But if you are nice in a friendly way then why would she ever move to romance?
A big mistake I think men make when it comes to woman is thinking women make the first move ever. They don't ever make the first move. *note - some women do make the first move; it's not a rule just a general correlation