Which ancient river valley civilizations do we still use today: Indus, Tigris and Euphrates, Huang He or Nile?
Depending on what you mean by "still use today" we use all of these civilizations. The civilizations that arose in these areas have had an impact that still continues to be felt on the people who live in those areas and/or on people around the world.
If you are asking which of these civilizations has had the most impact on the world as a whole, I would argue that it was the Mesopotamian civilization. It was in that civilization that writing first arose. Because of this, and because this was the first area to have things like extensive trade and urbanization, this area is called the "cradle of civilization."
If this is not what you mean by "still use today," please clarify the question.