Interesting thread.
I'm going to start off by repeating what someone else has already said - virtually any kage-level ninja can be defeated by virtually any other kage-level ninja. I'm going to make an arguement for each of the characters from the original post and then include some other characters that could win. I will end every arguement with who I think will win more than 50% of the time. I'm guessing that this could get long, so I'm only going to go four at a time so I don't give everyone information overload.
First up was Minato. In terms of overall intellectual ability, these two are nearly on par with each other. Due to his mastery of the sharingan, Itachi is one of the few people that would be able to find and keep track of the locations of every FTG kunai that Minato throws. On the other hand, Minato's speed should easily be enough to dodge amaterasu. I also doubt that Itachi's susanoo is fast enough to land a hit on him. Susanoo also makes it extremely difficult for Minato to land an attack. He could overcome this by dropping back and forcing Itachi to wear himself out, though whether or not he'd do this is debatable. The big advantage Itachi has is tsukoyomi. If Minato stands still long enough for Itachi to get it off he wins, but if Minato is continuously moving at speeds that are two fast to make good eye contact, that can be nullified. Again, whether or not he would do this is debatable. I see these two fighting a war of attrition, both are very capable of beating each other.
This is one of the few I will do that ends - Itachi 50% Minato 50% because of how close they are and how many possible variables there are.
Next is Hashirama. Based on hype Hashirama would win, based on feats that have been showed Itachi would win. I just haven't seen enough of Hashirama to make a definitive argument, but I would say he is capable of beating Itachi.
Not enough info to make a definitive judgement.
Third was Madara. Based on hype Madara shouldn't have a serious problem, based on feats this is a decent fight. I'm going to wait to make a firm judgement on this one until it is confirmed he can use the powers of the six paths, amaterasu, and tsukoyomi. I'm going to assume that he can, but until it is seen for certainty I'm not going to waste time making a big arguement on it.
Under this assumption, Madara should win more than 50% of the time.
Fourth is Hiruzen. Again, based on hype Hiruzen (prime) should win. Based on feats I don't see him beating Itachi more often than Itachi beats him. Like Hashirama, I can't make a great arguement because we have such little information on Hiruzen in his prime. I would GUESS he would be capable of beating Itachi, but I can't give a win percentage on such little info.
Not enough info to make a definitive judgement.
I'm going to take a break and post the next four a little later.