That's a fair substitution. I like to give a nod to Sartre and existentialism mostly because it's one of the few philosophical positions that's both accessible to those less familiar with philosophy as a whole, and as such it's had significant impact other cultural domains as well--though you are right, if our concern here is providing a list of those thinkers who made the most significant impacts to the field internally Heidegger is a much more important figure than Sartre (Nazism aside) and his thinking has spawned far more work and extensions than existentialism (as far as I know about anyway).