Judging by what we have seen from those two fighters Itachi simply pwns Minato... badly.
The fighters don't have detailed knowledge about each other and considering Itachi's Genjutsu feats Minato could be K.O'ed before he even knows whats happening.
Probably Minato should be able to put up a fight and win, but since other highly skilled Shinobi like Kakashi (who even has a Sharingan himself) where wtfpwned by Itachi's Genjutsu I can't base my vote on some unproveable assumptions.
Minato hasn't shown how he deals with Genjutsu so I will treat him like any other High Ranking Shinobi we've seen dealing with Sharingan Genjutsu... which doesn't realy benefit him at all.
Also Itachi's genjutsu >>>>>>>>>>>>>>>>>>>>>> Sasuke's. I fail to see how that part proves something.
rules say they don't know about each others' abilities,but they know about abilities as did they in the manga! Minato recognised tobi was madara,because he knew very well history and sharingan users,especially because he was obito uchiha's master. then he knows about sharingan and viewing itachi with it would make him think not to see his eyes. minato's speed would defeat itachi very well.
Not going to post my argument for who will win yet, but things that both sides should keep in mind.
Itachi's genjutsu: While Minato has shown no weakness against genjutsu, that doesn't mean he has shown any strengths against it either. Sarturobi, the God of Shinobi, was caught in a genjutsu that seems rather weak in comparison to Itachi's, so just because you are a Hokage, or because you are Minato does not mean you can't fall to a genjutsu, especially agains the God of Genjutsu.
Minato's Speed and Hirashin: While Itachi is extremely fast and has the Sharigan, he hasn't shown speeds to be able to keep up with Minato. Granted, he has a defense in Sussano which is fast enough to stop a lightning bolt, but he doesn't have the stamina to use Sussano every time Minato trys to strike him.
Hirashin: A baddass jutsu with one fault, that fact it requires a seal to use. Despite the fact that Minato can use this jutsu to his full advantage, if he is not careful he can Hirashin himself into a ball of Amaterasu. Just something to think about.
Itachi's MS techniques: For the most part are useless for how they are supposed to be used in this fight. Granted, Minato can't look Itachi in the eye unless he wants the greatest headache in the world a.k.a Tsyukiyomi. But Amaterasu is mostly likely useless (unless it's used as a trap) and Sussano is far too slow to strike Minato.
Summons: Useless as well. Itachi can put them in a genjutsu easily, or just dodge them. Not once has a large summon been able to truly turn the tide of a battle, especially with how slow and need to hit such a small and fast target.
Itachi's clones and handseals: If a Sharigan user can't see Itachi's handseals Minato has no chance. If he strikes a Bushin and it explodes unexpectedly, is he fast enough to dodge the explosion?
Minato can instantly teleport right next to Superman to hit him but before even his neurons exchange information superman can run, grab a burger and get back and punch Minato before he even knows he teleported o that other side.