None other than bitcoin. Why you keep on asking what's going to be the most profitable coin for each year if we know that it's always as bitcoin. Yes, the percentage varies from any other coins but bitcoin will remain as bitcoin and for me it's the most profitable coin base on my portfolio.

I like few altcoins but for me, it's still bitcoin so regardless of how much they will increase as long as I have more portion of bitcoin on my portfolio. Then, I wouldn't feel that much increase for those coins.