Take away Hashirama, Naruto, Sasuke, and Gaara and you have a correct answer.
Hashirama gets beat. Why? Because he has no defense against Itachi's genjutsu, nor does he have anything to defend against Amaterasu. Mokuton is too slow and burns easily.
Naruto - until the fox is a partner with him, like it is with Bee, he is vulnerable to genjutsu as that is his and Jiraiya's biggest weakness.
Gaara - Genjutsu again, and Itachi's Susanoo has the Yata mirror and without Onoki there to help him Gaara can do nothing against it.
Sasuke - of the ones you listed he is actually the most likely to beat him because his sharingan and blood relation to Itachi will help him the most against genjutsu. However his Susanoo is far weaker than Itachi's and that is what I think it will come down to. Also he is slower than Itachi and not as intelligent.
Hashirama (like Yamato) can bring out Wood from his body so he can use that to remove Amaterasu from his body if he's hit
he can block Totsuka and Yasaka Magatama with large wood techs which can even come from his body
Hashirama's wood release is all ranges and all Itachi's known genjutsu are short range so he wont be caught in it if he keeps a good distance.
He can crush Itachi with wood release that can grow from underneath his susanoo, like I said, it is all ranges.
When Kakashi faced Itachi the second time we learned something people seem to have forgotten-GENJUTSU DOESNT WORK ON SHADOW CLONES. Itachi said so himself 'no wonder you're not affected by the genjutsu, you're a shadow clone' now that Naruto's clones are faster than Amaterasu and all Itachi's attacks he can use them to attack Itachi without fear of Illusions and to bypass Susanoo, Naruto will send a chakra arm underground and pull Itachi out of susanoo then fling a rasenshuriken at him, killing him.
I've explaind Gaara's victory in the post above.
