Man: "Yes, you look great".
It's the only possible answer........
Suggested alternative:
Woman: "Do I look nice in this dress?"
Man: "What do you think?"
Woman: "I'm asking your opinion."
Man: "My opinion doesn't matter - it's your own opinion that counts."
Woman: "I'm afraid it makes me look fat."
Man (taking her by the shoulders and pointing her toward the nearest mirror): "Look, you need to fall in love with that woman right there. No external validation can ultimately make any difference in how you feel about yourself."
Such questions are a sign of immaturity and low self-esteem - the man should try being the grownup (for once) and helping her grow past this instead of ducking the question with some stupid white lie.
I like the TV commercial where the guy is occupied watching a game on TV, and his wife asks him, “Does this make me look fat?” And he doesn’t even look up and replies, “Uh-huh!”
On paper...that looks great.
Woman: "Do I look nice in this dress?"
Man: "What do you think?"
Woman: "That's it, you think I'm fat!!!"