Why does Marlow think that Kurtz was remarkable?

I think that Marlow and Kurtz have much in common. Both see the raping of the land and people by imperial power as a travesty. Marlow calls Kurtz "a great man", which automatically puts him at odds with other Europeans. I think Marlow was beginning to fall under the spell of the African jungle but left before it could take hold of him like it did Kurtz. I don't think Marlow feels he is as great a man as Kurtz, nor am I convinced he realizes Kurtz's limitations (like greed). Still Marlow feels changed by the Kurtz the man and his experience in the Congo.