There is no one right or wrong way to kiss a man on the lips. It depends upon the situation or the mood as to which kind of kiss is preferrabe and appropriate. He might want a soft gentle kiss when he is waking up in the morning or as a goodbye kiss before he leaves. At other times he might want a more passionate kiss when is trying to convey his love and desire to his partner.
There may be other times that he would like a harder more urgent kiss when he is engaging in sexual activity or perhaps simply having a make out session with his partner. When assessing how a man would like to be kissed on the lips you will have to first assess the situation and decide what is appropriate for whatever situation you are engaged in at the time.