NEW YORK — General Motors Corporation may rank as the nation's No. 6 company on Business Week's ``Market Value 1,000'' list for 1990. But on a new ``Performance 1,000'' list it occupies last place. The new list rates America's 1,000 largest companies by how much added dollar value they have created for shareholders. General Electric Company was No. 1 on the list, which was developed by Stern Stewart & Co., financial consultants. Using a complex measuring method, the consulting firm reckons that drug companies did best at adding value for shareholders, with Merck leading the way (3rd place overall). The discount and fashion retail industry was the second-strongest performer, led by Wal-Mart.