OBITO = TOBI
Ah this old beaten horse that died a millennium ago.
I have always and WILL always refuse Tobi = Obito as a legitimate theory.
Why? for starters Madara being alive is only a shock because he was beaten to within an inch of his life, there are any number of reasons he survived, sheer luck, Hashirama sparing him for whatever reason
(Their rivarly was much like Naruto & Sasuke's) and others I don't care to list.
Their fight happened 80 years ago, and Madara was quite young in those times, so him being about 95-105 years old isn't so insane when we saw Sandaime fight off Orochimaru as an old man as well.
The other thing is, we've already seen enough of his face to know that HE IS AN OLD MAN, Obito would only be about 29-30 in present day
(Same age as Kakashi) which if you can recall is not old at all.
The other thing is, the eye well personally I have no real way to explain that but I find the whole "Unique" thing with MS jutsus to be BS and anyone with MS can probably learn other MS techniques one way or another so whatever.
That and Itachi's words that EVERYONE can't seem to remember despite their importance.

Originally Posted by
Uchiha Itachi
"Madara is alive and well, as are his EYES and THEIR Power"
Now I do recall plurals mean
"more than one" so I have no idea what's up with the mask, his face could just be damaged who knows we already know Madara said he isn't what he use to be.
And Itachi did Say
"He is a Shell of his former self".
I'm not going to even bother bringing up the fact he didn't flinch or even recognize Kakashi in the slightest when they met... too late.
And there is also the fact Minato specifically indicated he fought Madara on the night of the Kyuubi attack, wut? Obito died and gained the power to summon Kyuubi in like a year? no that's just nonsense in my mind.
Then there is the fact he spoke of the entire Uchiha history, Rikudo and the Senju etc. His past with Izuna etc.
Because Obito..err I mean Madara would know this information from a first person perspective right?
There's other things I've been meaning to mention that go against Obito but I forgot them in amongst all the other overwhelming theory killing evidence sadly.