It was the best ever vs it is the best
“Ever” means “of all time”, but the exact meaning changes with the tense.
When used in the present, “ever” includes up to the present. When used in the past, it may include the present, or it may only include the time up to that point in the past.
So, “It is the best ever” means it’s the best of all time, up to the present. “It was the best ever” means either it was the best up to that point in time, and a better one may have happened since then, or it includes up to the present.
So, “Michael Jordan was the best player of all time” could mean that at he was once considered the best player of all time, but someone else has since surpassed him, or it could mean he is still the best of all time, just no longer active.