“You look good” is a compliment, yes. But it’s rather a very shallow compliment that people easily say to anyone that it had lost its value and meaning. Compliments that are commonly said don’t make an impact to the receiver anymore, so if you want to be remembered and if you want to leave an impression, you have to do better than that.
Here are some categories which can help you think of one:
Compliment his masculinity. Every man wants to be acknowledged for how much a man he indeed is. An excellent compliment that will draw him to you and would surely make his heart melt: “I feel so safe whenever I’m with you.”
A compliment that validates how much a man he is would make him feel secure about himself and in your relationship.
Compliment his character. Admiring his character sets him apart from all the men you’ve previously dated. This assures him that you are into him and no longer looking for somebody else. Compliments that begin with "I admire you for..." are a great way to start. An example: "I admire you for not losing your cool with that rude driver," or "I admire you for how you handled that unlikely situation."
When a man receives a compliment about his character, it will make him feel very special.
Compliment his ability to lead. Most men like to take the lead on things, whether it’s taking the lead on which route to take when going somewhere or handling a matter involving other people.
If he is a great leader, you could say compliments such as, “I loved how you took the lead on this,” or “I trust you.” You could also try saying “I’m on your side,” or “I would follow you anywhere.” These compliments would show how much you trust him.
Compliment his hidden traits. When you compliment a man’s talent, you’ll be just like everybody else. So instead, compliment the trait that made him good at his talent! That will make it much more meaningful. An example: “I like how determined you are in perfecting your music.”
When he hears a compliment that he doesn’t hear often, he will appreciate it more. It will make him remember you every time he picks up the instruments of his talent—whether it’s about music or any other passion. It will surely put a smile on his face.