Madara at the situation he is right now is not stronger than Itachi. Itachi first of all wouldn't want to attack him, because he was simply spying on him in order for him to gather valuable information about Akatsuki's motives (mostly involving Konoha) and propably about Madara's power.Well considering the fact that Itachi didn't kill Madara shows that Itachi knew Madara was stronger than him. Look at it this way after the massacre Itachi knew that Madara wasn't gonna stay still but he didn't do anything to Madara also Itachi implanted Amaterasu on Sasuke so that Madara can't reach Sasuke so Itachi knew that Madara might try to convince Sasuke so why didn't Itachi didn't kill Madara.The answer is most probably because Itachi knew that he couldn't beat Madara. Also Itachi told Sasuke that Madara was his mentor. And Minato defeated Madara. So don't need any other things to sayxd.
Madara said if Itachi knew everything (it seems that Itachi didn't have a complete image of Madara's Space-time Jutsu, something Madara hid well), he would be dead. In addition, Itachi had already business with Sasuke. He made a clear plan about dying in front of Sasuke, so that Sasuke attains new power (MS and then EMS) and become a hero of Konoha and I believe he hoped that Naruto and Sasuke would be the ones to counter and defeat Uchiha Madara. He may also have thought the possibility of Sasuke being manipulated by Madara and goes against Konoha, so he gave Naruto a gift (it may be a power that Itachi would originally wield, I like the jewel theory, but don't want to talk about it atm) that would help Sasuke realise what he should really do, defeat Madara and possibly get forgiven by the 5 Great Nations (which could happen, especially by the Fire and Sand Villages).
Madara did not have EMS on his fight with Minato, he only used the space-time jutsu. Minato was faster and more skillful and beat him. And because Minato beat a one-jutsu spammer (that's how Madara is atm), doesnt' mean that "Madara is the strongest..mmm he was beaten by Minato, so...ah! Minato>Madara>All -> Minato>All.
I may be an Itachi fan but I have my own arguements. Just to make it clear.
PS: Sorry for typoz, I'm in a hurry xP