While elves and dwarves did exist in Nordic mythology well before Tolkien penned them, they in no way represented the elves and dwarves that we take as common place today. He created the cultural models that most use today when writing "High Fantasy."
People like George R.R. Martin probaly would not have been effected by a lack of Tolkien in a structual sense, but who knows where he draws his inspiration, and who knows if fantasy could even be a profitable endevour without Tolkien.