A tough question since the Packers have been in the NFL since 1921 and the Cowboys since 1960. The Packers have won 12 NFL championships and the Cowboys have won 5. All in all, I would say both teams have a very rich history and it would be very difficult to say which team has had the most success.
As of November 15, 2009, they are 1-6 against the Green Bay Packers at Lambeau. After "breaking the jinx" for their first Lambeau win on September 21, 2008, the Cowboys suffered a reversal of fortunes on November 15, 2009, losing to the Packers 17-7.(see the related link)
Green Bay has a 7-and-12 record against the Dallas Cowboys in games played at the Cotton Bowl, Texas Stadium and AT&T Stadium. In games played at Green Bay's Lambeau Field, the Packers are 9-2. In Milwaukee, their record against the Cowboys is 2-3/. Green Bay also won an important game in Dallas that did not involve the Cowboys. On February 6, 2011, the Packers represented the National Football Conference in Super Bowl XLV at the Cowboys' arena. They won the Super Bowl, beating the Pittsburgh Steelers 31-25.
Since the Super Bowl era began in the late 1960s, both the Dallas Cowboys and the Green Bay Packers have been in the same league or conference. As a result, only can reach the Super Bowl in any given year
Since 1967, the Cowboys are 1-6 in games played at Lambeau Field, but 3-1 in games played in Milwaukee.
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Since the 2009 season, Dallas has played its games in Cowboys Stadium in Arlington, Texas.
The Green Bay Packers have won three National Football Conference championships since the National Football League's merger with the American Football League in 1970. Green Bay won the titles in 1996, 1997 and 2010.
430 games won
Since 1960, the Cowboys and the Colts have played 16 times, which includes regular season and postseason games. The Cowboys lead the series 10 games to six.
the packers
Since the Dallas Cowboys were founded in 1960, they have appeared in 10 NFL Championship games: 1966 - Lost to Packers 1967 - Lost to Packers 1970 - Lost to Colts 1971 - Won against Dolphins 1975 - Lost to Steelers 1977 - Won against Broncos 1978 - Lost to Steelers 1992 - Won against Bills 1993 - Won against Bills 1995 - Won against Steelers