Gandalf literally sang the universe into existence with his brethren. No D&D wizard ever did that. And one of Gandalf's siblings moves the sun through the sky, and another the moon. Yet another raised Numenor from the sea floor and raised it up as a island nation and fastened another island to the sea floor when it reached Aman. Melian another like Gandalf shrouded an elf nation such that not even Morgoth could find it and her daughter who was half-Maia, was able to use her power to overcome Morgoth and put him to sleep. Gandalf is one such as them and has a great deal of power that he didn't show, because he was instructed to limit himself while in Middle Earth. He is NOT 6th level.