Just 4 million a year after release? The game definitely deserves to sell 10+ million.
Tekken 8 sold 2 million copies in its first month alone.
MK1 has sold nearly 3 million copies in less than two months.
But the guys at Capcom seem to be pretty pleased about it. So, I guess it should be Ok.
Personally, I have been a SF/Tekken fan since childhood, three decades ago. So, I bought them both - SF6 and T8 - as the characters bring nostalgia to me.