where did it say the younger son > older son. The only time the younger beat the older is when Hashirama killed Madara but we see how that turned around...
Will of Fire (Love) > Curse of hatred (power)
Rikudo confirmed this by choosing the younger son as his successor
Younger Son (will of fire) > Older son (curse of hatred)
Hashirama (will of fire) > Madara (curse of hatred)
Naruto (will of fire) > Sasuke (curse of hatred)
Madara became stronger than Hashirama by obtaining his powers and DNA, thats like Sasuke taking naruto's DNA and powers becoming stronger.
Naruto will succeed Rikudo's wishes and bring peace.