Ha..I see many of you are feeling sorry for Hiruzen and calling him the weakest you silly little fan boys. Yes Hashirama is the strongest hokage but Hiruzen is number 2 and is the next in command. Most you were wrong about tobirama being more baws than hashirama and you same children are underestimating hiruzen in the same mannor.
First of all Hiruzen was one of the most powerful shinobi in history, so much so that he was admired as the God of Shinobi (忍の神, Shinobi no Kami) in his prime, and was said to be the strongest Hokage that Konoha has ever had.[1][20][21] Even in his old age, he was also said to be the strongest of all the five Kage at the time of his death.[22] Enma commented on his battle with Orochimaru, saying that it was "miserable" compared to his prime, even though he had clearly been able to hold his own against Orochimaru and two former Hokage without losing his composure. Even in his old age, his chakra was noted for being very strong, causing a dense effect on the atmosphere when released;[23] furthermore, he was known for having immense reserves of chakra in his youth.[24] He was also the longest living and longest reigning Hokage. Hiruzen also had keen senses, being able to track down the former Hokage under Hashirama Senju's Bringer-of-Darkness Technique.
secondly, Hiruzen was also called The Professor (プロフェッサー, Purofessā), due to his mastery of all forms of shinobi combat, and his vast knowledge of techniques, purportedly knowing all the techniques within Konoha.[26] In the anime, even Danzō, Hiruzen's life-long rival, openly acknowledged the Hokage's sheer prowess in utilising any technique as unsurpassed.[27] His title also came from creating a considerable arsenal of original techniques; one of which was the Shuriken Shadow Clone Technique. With this technique, he could create a thousand clones of a single thrown shuriken in an instant to overwhelm the opponent with the extreme difficultly in evading them all. This method also meant that he didn't have stock up on a lot of shuriken. To watch over the village, he would use the Telescope Technique, allowing him to observe others through his crystal ball over long distances.[28] Despite his diminished reserves of chakra in his old age, he also showed great chakra control, needing only the minimum amount of chakra to use each technique.
Also, Sarutobi was highly skilled in elemental ninjutsu, using Fire Release and Earth Release. Fire Release: Fire Dragon Flame Bullet allowed him to exhale a powerful stream of fire from his mouth. Earth Release: Earth Flow River created a river of mud beneath the opponent to throw them off balance, and he could use the mud with Earth Release: Earth Dragon Bullet, which creates a dragon's head that launches mud balls at an opponent. He had also been shown to be adept in combining elemental techniques, as seen when he ignited the mud ball projectiles with Fire Release: Fire Dragon Bullet, creating a volley of hot mud that can melt nearly anything. Earth Release: Earth-Style Wall allowed Hiruzen to spit a stream of mud that solidifies into a protective shield. And Hiruzen also had a personal summon: Monkey King: Enma, who was capable of turning into a diamond-hard staff, which could alter its length and width at will, or become a cage to protect the summoner. The staff was Hiruzen's weapon of choice as he showed great proficiency in wielding it; he successfully pushed back Kurama with it during its attack on Konoha.[29] Enma could also manifest parts of his body and attack an enemy with his claws and fangs, which added an element of surprise.
Finally, In terms of taijutsu, Hiruzen displayed a very high level of it in old age. He was able to counter Hashirama and Tobirama in close combat, despite them being in their prime in the Summoning: Impure World Reincarnation. He could lay an explosive tag on each of them without them or Orochimaru who was controlling them even knowing. After summoning Enma, he could break Hashirama's Wood Release branches with ease.
Even when robbed of his sight from the genjutsu Bringer-of-Darkness Technique, he could still defend himself from Hashirama's and Tobirama's assaults, blocking all their attacks to prepare for his Dead Demon Consuming Seal. After sealing both former Hokage, he faced Orochimaru in single combat. Despite his sealing parts of his soul away in the Shinigami, as well as fighting for a prolonged amount of time before he engaged Orochimaru one-on-one, he effortlessly disarmed him of his sword.
Keep in mind he is not young like the others yes but he has unlimited chakra and has been around far longer than the others to see more events that have transpired. He is now free to use unlimited chakra and more than likely knows the seals that can release his edo contract as he like kakashi can use other techinques he sees as he has already demonstrated in the greatest battle of naruto to date which is hiruzen vs oro and 1st and 2nd. Yes they were not full strength edo tensei but he was also older and figting under extreme stress and more than one opponent.
here is the order :
1st best hokage = (Hashirama god of shinobi)
2nd = Hiruzen (the man is a nijitsu god)
3rd = minato (his own student almost killed him in his prime)
4th and least strong = tobirama (his temper is major weakness just like you fan boys)
Keep in mind that the original sage of 6 paths is the strongest of them all.