Edo Madara is ranked ahead of Itachi, I have him 2 or 3, and Itachi is a different tier at 4... that said, there are some ways Itachi can win. He has some one shot techs that Madara may not be able to block (or expect, if no advanced knowledge), and can survive quite alot thanks to Susanoo and Yata Mirror.
1) Prime Itachi has Shi Sui's eye. I guess some people might want to gimp Edo Itachi out of it, if so then Itachi might be better off without being an Edo. But it's very questionable if the no feat limit fallacy can protect Madara from Koto, I'm not sure it can.
2) He has the Totsuka blade, and Madara doesn't know what it is, and can't really block it (it's etheral, and is described as being able to even hit non-physical things like spirits).
3) He has Izanami, so as long as he can survive long enough to form a loop, Madara can be trapped in it (and then while in it, Itachi Ameratasu's him before he figures how to escape it, and/or seals him).
4) He has Ameratsu, and until Madara actually demonstrates this ability I'm not granting it to him, which means he can toast alot of Madara's attacks... I think Susanoo will defend against this, so Madara is fine, but it's not something that's super easy to counter unawares.
5) He has a one shot Genjutsu of his own, and has been shown to be maybe the strongest genjutsu user in the manga... maybe he can beat him with genjutsu... it's unclear, but it's certainly not out of the question.
Tough for Itachi to win, but he does have a few methods.
