SuperMarioGamer
So what would you say to such a painter and what would you think of him/her?
The same thing I said to you. I have often heard it said that only a born artist can endure the process of becoming one and I think that statement is absolutely true. Learning an instrument is hard. Learning to write music on it is hard. Learning both well enough to be able to then write the exact music you hear in your head is even more difficult and takes tons of hard work. Without a passion for the instrument and without a passion for the process of learning it, you will fail. Guaranteed.
And here's the #1 clue that you will fail. You're here asking the question instead of just going off and doing it. If you truly had what it takes to accomplish what you describe, you wouldn't be asking anyone if you could could succeed at it. Instead you'd be off working on it and no one would be able to talk you out of it.
But you're not doing that. Instead, you're on the internet asking complete strangers who have never met you and know nothing about whether or not they think you have what it takes to succeed at going from zero to youtube music star. And the answer is easy. If you have to ask the question, then you already don't have what it takes. Sorry champ.
My advice: Go find something that you want to do so badly, no one could ever talk you out of trying. And then go do it. And when you feel like you want to come back here and ask about being a youtube music star again, go do that other thing some more. Do it until your fingers bleed. Then do it some more. Do it until you can't stay awake any longer, then do it more.