Winning the Super Bowl is greatest accomplishment an NFL player can experience, and it can never be taken away. That being said, it is very difficult to repeat, or even get back to the game the following year (the last team to do it was the Patriots in 2004). To illustrate how difficult it is, just look at the Giants, who have experienced disappointment in each season following a trip to the Super Bowl.
Here's how the Giants fared the seasons after their four championships:
Super Bowl XXI: Finished last in NFC Eastern Division with a 6-9 record in 1987. It was a season marred by a work stoppage and replacement players. The Giants did not take the situation as seriously as some other teams, such as Washington, who went on to win the Super Bowl that season. The Giants began the season 0-2 before the players went on strike in Week 3, which was then cancelled by the league (the Giants were scheduled to play the Dolphins in Miami. The owners stocked their rosters with replacement players (aka scabs) for the next three games. The Giants lost all three games in miserable fashion. The regular players returned in Week 6, but at 0-5, they didn't have much of a chance to compete. FYI....Lawrence Taylor and QB Jeff Rutledge crossed the picket line to play in the Week 5 loss to the Bills in Buffalo. Taylor said he simply couldn't afford to lose another paycheck, estimated around $60k per game.
Super Bowl XXV: Finished fourth in NFC Eastern Division with 8-8 record in 1991. Bill Parcells retired in the offseason, but he waited until May to do so. Bill Belichick was gone - off to Cleveland - and Tom Coughlin was hired at Boston College. GM George Young promoted Ray Handley to head coach and the wheels would off shortly after. Handley chose Jeff Hostetler to be his starting QB over a healthy Phil Simms. Hostetler broke a bone in his lower back in the Week 13 win over Tampa Bay and was gone for the season. Simms took over and the Giants went 2-3 the rest of the way. After the season, Bob Tisch bought 50% of the club from the family of the late Jack Mara, Wellington's brother.
Super Bowl XLII: Lost to Philadelphia 23-11 in Divisional Playoff in 2008. The Giants won 10 of their first 11 games and looked like they were on their way back to the Super Bowl when WR Plaxico Burress shot himself in the leg at a NYC night spot. The Giants finished 12-4 and had home field advantage in the NFC Playoffs, but they never really recovered from the Burress incident or the subsequent loss of his services.
Super Bowl XLVI: Finished second in NFC East with 9-7 record. They failed to make the postseason after beginning the year at 6-2. Superstorm Sandy hit on October 29, devastating the NY and NJ coastal communities and disrupting life in the NYC Metro Area. Everyone was affected, and like many in the region, Giants players and coaches were driven from their homes. The Giants went 3-5 the rest of the way, losing a crucial division battle by one point in Washington and then getting whitewashed in Atlanta and Baltimore.
The Giants lost Super Bowl XXXV to the Baltimore Ravens, 34-7, in what may be the most disappointing game in the history of the franchise. The 2001 season began with a Monday night loss in Denver. The next day, the World Trade Center was attacked, forcing the NFL (like most other entities) to temporarily shut down and focus on the bigger picture - getting America back on it's feet. The Giants won their next three games after the league resumed play on Sept 23. With two games remaining, the Giants were 7-7 but lost their final two games to finish at 7-9. DE Michael Strahan set the NFL single-season sack record (22.5) with a sack of Green Bay QB Brett Favre in the final game of the season.