The NFL has so few games that every game matters significantly, and anyone can win any given week. It is so hard for players and teams to be consistently great year in and year out because of injuries and salary cap issues. Great offenses and defenses are broken up every year due to the salary cap. It's bad for chemistry and for the players, but it's great for the fans because they know their team can go from out of the playoffs to Superbowl champs in one season. Lets take the Atlanta Falcons this past season. The team was in turmoil, they lost their best player in Michael Vick and traded one of their top players (Deangelo Hall), and they only won 4 games the year before. Everyone thought they would be in for a long rebuilding process and competing for the leagues worst record, but.... "not so fast my friend". This is the NFL. Things change very fast.
In the MLB, with the rare exception like last years' Tampa Bay Devil Rays the teams with the highest payrolls win the most and make the playoffs. Teams like the KC Royals, Brewers, Marlins, and Pirates who don't have the same money to spend like the Yankees, Red Sox, Dodgers, and Angels virtually have NO chance of making the playoffs, let alone winning the World Series. This is what football will become without a salary cap. Some players have the misconception that money will be flowing like water for everyone, but that's not true. Just like when there is no ceiling, there is no floor. Some teams will have payrolls soaring past $150 million while smaller market teams will spend drastically less . In addition, players won't be eligible for free agency until after 6 seasons. The NFL is a very physical game, and injuries happen that end great players careers' early. Benefits will be slashed and so will post career health care which is so vital for former players and their families. The big money will only be able to be made after 6 years, and that's if a team with a lot of money is in need of your position.
An uncapped year is bad for the owners as a whole (only a few teams like Cowboys, Redskins, Bears, Giants) will be able to remain competitive. An uncapped year is bad for the players as a whole as well for short term and long term reasons. I love football and I want the NFL to remain America's BEST and favorite game. I love the competition and not knowing who will win a game before it starts. I love the NFL for the same reasons I love the NCAA tourney - winning the national championship is achievable/possible for any hard-working team.