Well here's my argument.
Tobi Vs Minato (Already happened) - Tobi had to flee, and Accepted minato as to be worthy as to hold the 4th hokage Moniker, But if it's Tobi right now then Tobi, IDC if minato has FTG, tobi is too haxed.
Madara VS Hashirama (Fight done and Dusted) - I personally still think the same outcome, Hashrima takes this by high / Very high difficulty.
Itachi VS Naruto - If its naruto as he is now then NARUTO, But if it's normal then IMO Itachi due to the fact he isn't Diseased. So i think itachi

Due to his intelligence and knowledge on the battlefeild, where as naruto is still learning. And hes a Sharingan master and very advanced in Taijutsu.