I don't know if anybody considers him a great coach. I think many people consider him to be a pretty good coach. I don't think it is particularly easy to go 113-40, with a national title game appearance and 3 other top 10 finishes, at Notre Dame in today's game.
What he's done so far at LSU I think is less impressive than what he did at ND, although he's completely capable of winning a national title at LSU because of the program LSU is. He had a Heisman-winning QB last year yet still lost 3 games because the defense was so bad, and it doesn't exactly appear to be fixed so far this year. The two coaches they had before him are complete clowns and played for 3 titles in 13 seasons, winning 2 of them. I think he also gets more heat at LSU because he's an odd cultural fit there.
Also, the vast, vast majority of successful coaches are beating teams with less talent. The entire point of the sport is to take the field with more talent than your opponent. How many games did Saban or does Kirby win with less talent than the team he's playing?