What's the difference between stroganoff and goulash?
Traditional goulash is a stew/soup, usually using a cheaper cut of meat suited to slow cooking. It usually contains potatoes and other vegetables, as well as noodles. 

A true stroganoff consists of paprika-dusted fillet steak quickly pan fried with mushrooms and onions in a sour cream and brandy sauce. It is usually served with rice.

I understand that in the US stroganoff can also refer to a stew made with similar ingredients as the traditional dish, and is served with noodles. This, coupled with the shared use of paprika, is evidently where the line blurs.