Tread lightly here. Women are often turned off by a guy complimenting them. "Oh, it's a line. "He's a dog."
We are cautioned about sexual harassment, abuse, and using one's Job (position) to gain favors. All true and to be respected.
BUT: In romance movies and hopefully in books there comes an appropriate time where the two protagonists complement each other (or one does and it is appreciated). So what's the difference? They're either on a level playing field or recognize the remark as sincere. But there's magic here. They feel the same way. Yep, that's how romance works on one level, mutual attraction. So actually saying that you are attracted becomes an affirmation to the other that they are loved or at least desired by someone they desire too.
There may not be a better natural feeling than knowing that the other appreciates you as much as they appreciate them. This assumes a lot of info has been collected to jump to the conclusion in a romance that you are truly loved. When this happens picture fireworks, because that's the ball game.