Both alistar and amumu are good higher tier tanks. Shen is also a good tank with cc.
The pros for amumu are that he has an amazing ult that can stun an entire team, has a skillshot that can stun, has good aoe damage, and has alot of health. Cons are that 1 of his abilities is a skillshot, his ult is greatly reduced by merc treads, and he requires good team communication to use properly.
The pros for alistar are that he can heal for sustained pushed, has 2 forms of cc in headbutt and pulverize, and his ulti makes him near invulnerable for superior tanking. The cons are that he has a slower base speed, slower attack speed, relies a little to much on the summoner spell flash, and has longer cooldowns on headbutt and pulverize.
The pros of shen are that he has an aoe taunt, he has a damage mitigation ability, his voral blade hurts alot and has a decent heal attached, he can farm rather easily, if he is focused, his passive makes him deal alot of damage fast, and his ulti is a teleport and a shield for himself and an ally. The cons are that with the recent nerf, he's not as gamebreaking, he only has 1 form of cc, his taunt is a skillshot, his feint ability isnt very good, and he has a lower base hp for a tank.
The pros of blitzcrank are that if you land the rocket powered grab its basically an instant kill, he has very good damage for a tank, he can push well, his passive gives him a mana shield, he has 2 forms of cc in rocketgrab and powerfist, he can chase or escape decently well, and his ulti is not only a passive damager, but an activatible aoe damage. The cons are that he can be focused down easily, his skillshot is moderately hard to land, his tanking ability in terms of eating damage is sub-par, and his escape mechanism also slows him after a few seconds.
Overall, these tanks are all pretty good. I would recommend either shen or amumu.