I would guess the Minnesota Vikings for the NFL since they have been in the league since 1962 and never won it all (unless you count the 1969 NFL championship they won before losing to KC in SB IV).  The Cardinals won it all in 1947, and the Seahawks were est. in 1976. The Astros/ Colt 45's have been in MLB since 1962 and have never won the WS.