Westword has an interesting article, that while focused on some Denver restaurants, provides a brief explanation of the difference between ramen and pho. I've had and love both, but I've never seen pho at the store for 20 cents a pack.
Here's a snippet:
In a bowl of ramen, the long, curly noodles are made from wheat, which has the structure-giving gluten that pho's rice noodles do not. Ramen stock is darker, richer and cloudy, often made from pork bones cooked at a rolling boil, whereas the base for pho is traditionally made from beef and scented with star anise, cinnamon and charred ginger.