When Menelaus returns from the Trojan War, he is victorious and has reclaimed his wife, Helen. Helen had been an unfaithful wife, unlike Penelope who remains faithful to Odysseus for the entire twenty years he is gone. Menelaus has forgiven an unfaithful wife, while Odysseus can rejoice in a loyal wife.
Agamemnon is murdered by his wife's lover upon his return from the war. This disloyalty is avenged by Agamemnon's son when he kills his mother's lover. Again, Odysseus has a failthful wife (unlike Agammemnon), but he DOES have a loyal son (like Agamemnon).
Telemachus is always loyal to his father even though he has not seen him since he was an infant thown in front of a plow. His loyalty to his father makes him a threat to the Suitors, and so they wish to get rid of him. When he returns from visiting Menelaus, the Suitors, led by Antinous, plot to murder him. He is not shown proper respect as the son of the King of Ithaca.
When Odysseus returns, he comes in disguise to learn who has (and who has NOT) been loyal to him during his long absence. Unlike the others, who come home as "themselves", Odysseus uses stealth before announcing his arrival. This prevents him from being killed, like Agamemnon, by someone who wishes to steal his wife.