Michael Jordan turned 50 on Sunday — a milestone that spurred a number of tributes to his accomplishments on the court. But perhaps his most impressive achievement is the fact that he reportedly earned $80 million last year in endorsements, outpacing all other sports figures in that department by a wide margin, even though he hasn’t played in nearly a decade.

Assuming Forbes magazine’s annual list of highest-paid athletes and recent reports about Jordan’s earnings are accurate, he made $25 million more in endorsement money last year than any other current athlete (although he’s not represented on the list because he’s retired). As a marketer, I find it interesting to look at the breakdown of where the endorsement money is being spent. The top of the list includes:

• Tiger Woods – $55 million
• Roger Federer – $45 million
• Phil Mickelson – $43 million
• LeBron James – $40 million
• David Beckham – $37 million
• Kobe Bryant – $32 million
• Rafael Nadal – $25 million
• Christiano Renaldo – $22 million
• Maria Sharapova – $22 million
• Usain Bolt – $20 million

Surprisingly, at least on the surface, there’s nobody represented near the top of the list from America’s most popular sport. In fact, you won’t find an NFL player ranked in the top 20.

Peyton Manning tops the list of NFL stars with $10 million in endorsements, followed by his brother Eli at $8 million and Tom Brady at $4 million. It drops off significantly after that, with Michael Vick at $2 million, Larry Fitzgerald at $1.5 million and a handful of players around $1 million, including Darrelle Revis, Adrian Peterson and Ben Roethlisberger.

The NFL dominates television ratings and has become a year-round topic of interest, as witnessed by the buzz that will surround this week’s scouting combine, next month’s start to free agency and April’s draft. So, why doesn’t the NFL’s popularity translate into more lucrative endorsements? I’ve heard several theories mentioned, including:

• Football players are less recognizable because they wear helmets on the field
• Football is a team sport and it’s harder for one player to stand out
• The NFL schedule has only 16 regular season games compared to 162 in baseball and 82 in the NBA
• Football players tend to have shorter, more uncertain careers
• The NFL doesn’t allow its players to fully showcase their personalities

I’m certain all of these things factor in, but I think the answer is much more simple. Despite all of the attention the NFL generates here in the U.S., it simply doesn’t appeal to a global audience like other sports. Just look at the list above and you see golf, tennis, basketball, soccer, and track and field represented — all sports that are widely played around the world. Furthermore, only four of the top 10 are Americans.

It’s not that the NFL hasn’t tried to to grow the sport internationally. The first NFL pre-season game outside North America dates back to 1976, the league’s “American Bowl” series has seen 40 pre-season matchups around the globe and the World League of American Football had franchises in several European countries in the early 90s. Perhaps part of the problem was branding – calling something “American” is probably not the best way attract a worldwide fanbase.

I give the league credit for continuing to try. They have upped the ante by playing a regular season game in London every year since 2007, more wisely named the International Series. And next season, London will host two regular season matchups, including one of the Minnesota Vikings “home” games.

Making strides in the UK is a nice start, but global relevance is still light years away — ensuring the NFL’s biggest stars will lag far behind their counterparts in other sports when it comes to winning the endorsement game.