By KEN SWEET, AP Business Writer NEW YORK (AP) — For 50 years, the American Express "Green Card" has been the card many people wouldn't leave home without. Launched in 1969, the Green Card gave travelers a sense of importance they didn't feel carrying travelers' cheques. For many people, it was their first AmEx card. Over time, however, the Green Card became neglected in favor of its fancier siblings,