After some thought and ideas... I came to the conclusion that the true identity of Uchiha Madara is Uchiha Obito. Again this is only MY opinion, that doesn't mean is less real or less fake. How did I got to that? Well, for starters, let's say that Madara and the 1st hokage just ended the battle. The 1st hokage, believing that Madara is dead, leaves him. Madara is totally bated up. He knows hes dying. he needs a new body but not just any body a body of an uchiha. after some time he finds Uchiha Obito (still don't know how he did it he must have some kind of jutsu or orochimaru). That would explain some things like age, appearance and why his right arm is fake. For those of you who don't know who is obito read the manga or episode of kakashi chronicles. Again, this is only MY opinion. Feel free to comment and discuss..hell, troll it if you feel like it.