Answer:
He is trying to placate Calypso so she will not make his journey more difficult.
Step-by-step explanation:
Calypso is a goddess and she wants him to stay. So, he calls her by "Oh! Great goddess, don't be angry with me, please". He acknowledges what Calypso has said to be true (including regarding his wife) and even acknowledges Calypso's beauty as much greater, but he is a diplomat and, even though he isn't really lying, it isn't really an insult (to say that a goddess who will never age is more beautiful than an old/mortal woman). He just wants her to be less angry.