Riley won 2 Grey Cups in Canada, and was the coach for 4 of the 7 seasons (ever) when Oregon State won at least 9 games.
I'd agree that he wasn't the best fit for Nebraska, but I don't know if I'd say he's never won. His only college gig other than Nebraska is a place where most coaches haven't won. Oregon State had been to 9 bowls between 1939 and 2002, and he took them to 8 bowls between 2003 and 2013.
Again...bad fit for Nebraska, but I think he deserves a little more credit as a college coach in general than people give him.