Individually, without a doubt. In a free for all, you're both overestimating the 1st and underestimating the other Kage.
I think Hashirama will solo them even if they will work together against him. I guess your view is a bit one sided when you say that Muu could turn invisible, fly up and clear it with a Jinton. Hashirama was the strongest man of his time, leader of Senju and grew up in a time of war, fighting victims which were stronger than those Kage. Killing someone that easily is mostly the case with fodders, whose only purpose is to endure certain techniques for showing their effect. I'm sure the current Kage are are by far better then this team, as they were five, had a great healer and Gaara, whose abilities exceed those of his father, just as Oonoki was a better supporter than Muu could be. Yet Madara, who fought both sides said not only once Hashirama to be by far superior to them. It's clear as day. Creating a flower tree world would crush anyone apart from Muu, Muu could probably carry one of them, while the rest would helpless wait for their downfall. With a few Mokuton Bunshins which are capable of using the originals techniques, he would dominate the battle, as they'll not only outnumber them, make use of Ninjutsu but also of the A-Rank Genjutsu Bringer of Darkness. It's a whole different story, if those Kage will have to face 2-3 Mokuton Bunshins, of which each one will use the Bringer of Darkness.
If they will fight in a zigzag, it will even be easier for Hashirama.
tsunade beat 2nd mizukage where minato wtf :rofl:
