Croco boy does have an amazing df maybe if he could awaken it could be even stronger
I believe Crocodile was Awakened in Alabasta. To me, Awakened Logia's alter the very climate/ecology of the area around them, until the user faints/dies. Crocodile was running massive sandstorms in Alabasta, similar to Akainu and Aokiji leaving Punk Hazard a frozen and fiery hellscape. It was only when Croc fainted that the sandstorms went away.
I think Crocodile needs to work on his Haki/raw physical strength, Luffy beat him because he was physically stronger, Croc's DF mastery was much greater.