Chuck Berry was great and a musical genius but he did not invent rock 'n' roll as many people say.
His songs are all very similar. Rock 'n' roll with a very country sound.
He came about 1954 - 55
Elvis' music however is extremely varied. Even his rock 'n' roll falls into different categories like r&b, swamp rock, rockabilly, rock.
As well all the other genres he went in to like ballads, blues, jazz, gospel and funk.
He came out in 1954.
In my opinion Elvis is by far the greater artist. He is the most successful solo artist of all time, a much better singer and performer, and he is the king after all.