Was Jim Kelly a great NFL QB? Yes.
Was he better than Joe Montana, Troy Aikman, Tom Brady, etc....? No.
If Jim Kelly had gone 4-0 or even 3-1 in those Super Bowls...where would he be in the pantheon of NFL QB's....probably top-10?
Record in championships has to matter. Who cares if a player goes 8 times, but only wins 2-3 titles? Isn't it about winning? Yes, it is a great accomplishment, but winning is what the sport is about.