Would be an interesting fight at the start off. (Assuming Madara played around a bit.) It really depends on how Itachi opens the fight (Tsukuyomi; and if Madara would be able to genuinely break out of it-- I firmly believe that Sasuke "broke out of it" ONLY because it was all part of Itachi's plan to make it seem like Sasuke had a legitimate chance of beating him)... Butttttt... With all of that being said... 9.9 times out of 10, it goes to Madara in every other scenario.
Edit: Oh... And... Madara being the cocky guy that he is, he also has a very real chance of losing *IF* Itachi quick shotted him with his Sword of Totsuka and sealed him away. That's a very real possibility.