Formal:
* Bonjour, bel homme. (Good morning, handsome man.)
* Bonjour, monsieur. (Good morning, sir.) This is the most formal option and doesn't directly mention his attractiveness.
Informal:
* Bonjour, beau gosse. (Good morning, handsome guy.)
* Bonjour mon beau. (Good morning, my handsome.)
* Bonne matinée, mon chéri. (Good morning, my darling.) This option is very affectionate.
You can also use a playful greeting like:
* Bonjour, t'es beau ce matin! (Good morning, you look handsome this morning!)
The best option will depend on your relationship with the person and the context of the situation.