In Santorini, does a god power replace original win condition
You can win by reaching the third pillar with both those gods.

Per the rules, the win conditions of Chronus and Eros both start with:


  You also win if ...


Also indicates an additional win condition.  Completing either will earn you the win.

This is spelled out on page 2 of the rules as well


  Additional Win Conditions are
  specified by some God Powers. In addition to
  being able to win by moving up onto the third
  level during your turn, you can also win by
  fulfilling the “Win Condition” described.