Friend D. Travers Scott has a great entry on his blog about the thrill of seeing a stranger reading his book.
Success has many definitions. Selling my first story was a victory. Holding a copy of the anthology made it real. Going into a bookstore with a friend, pointing at the shelves, and saying, "I'm in that one, that one, and this one too," is a jolt of happy reality.
None of that is at the J.K Rowlings "richer than the Queen of England" level of success, but I'm sure that the first time Rowlings spotted a Harry Potter book outside a bookstore, it gave her a sense of satisfaction that she still remembers. Hopefully, one day I'll see someone reading one of my books too. That's all this writer wants.*
*although I wouldn't turn down fantastic success or fortune either.