How might Gatsby not be great??

Gatsby certainly has his flaws, perhaps even tragic flaws. Gatsby has created his whole world around Daisy, who is herself an extremely flawed character. Daisy represents a fantasy. Gatsby believes he was destined to marry Daisy. Daisy, believing Gatsby to be dead, married Tom. Daisy represents a world that never really happened. Gatsby attempts to re-create the past so that the five years they have been apart never took place. Unfortunately Gatsby can't buy off reality. I don't think Gatsby ever really changes. Nick advises Gatsby to leave Long Island until the scandal of Myrtle's death has quieted down. Gatsby refuses, as he cannot bring himself to leave Daisy: he tells Nick that he spent the entire night in front of the Buchanans' mansion, just to ensure that Daisy was safe. He tells Nick that Tom did not try to harm her, and that Daisy did not come out to meet him, though he was standing on her lawn in full moonlight. Gatsby simply cannot let go of his illusion.