The New York Giants generate more online buzz than any other National Football League team but garner just about the lowest local-TV ratings. Every grandmother in Cincinnati watches the Bengals when they're on TV, but the rest of the country doesn't seem to realize they exist. And then there are the Jacksonville Jaguars, who, no matter how you look at it, don't seem to have accumulated much fan support of any kind.

THE MORE THINGS CHANGE: A 1976 lunchbox shows some of the NFL's iconic team logos. Diane Fields for The Wall Street Journal

The NFL season begins Thursday night as the Super Bowl champion New Orleans Saints host Brett Favre and the Minnesota Vikings. This game will pull a national-TV rating that's huge by sports standards: If precedent holds it will likely outdraw most games of Major League Baseball's World Series.

But as prolific as the NFL has become in its ability to divert eyeballs to televisions, there are substantial differences in the relative popularity of its 32 teams. Everybody knows the Green Bay Packers have a devoted and frostbitten following, for instance, but what about the Atlanta Falcons?

In a first-of-its-kind study performed this summer, Nielsen Co., the media-research firm, developed a system for ranking the popularity of NFL teams based on each team's local and national TV rankings, how often they're mentioned on the Internet and how many visitors they attract to their official websites. The report, dubbed the Nielsen Sports Media Exposure Index, is the company's first attempt to classify pro-football teams in this manner.

Not surprisingly, the survey confirms that America's team is, in fact, "America's Team," as in the Dallas Cowboys. In the final ranking, they were a stunning 23% more popular than the No. 2 team, their old rivals the Pittsburgh Steelers. The Giants were next, followed by three of the four teams in the NFC's North division: the Chicago Bears, the Green Bay Packers and the Vikings.

The Cowboys are on top in part because they're popular to begin with. Nielsen counted the total number of viewers of a team's national broadcasts from last season, rather than the average. So in most cases the more a team was picked to play in front of a national audience, the better it did. The Cowboys, who led the league last year with six national appearances, had a whopping 117 million viewers.

Bill Wanger, the executive vice president of programming and research at Fox Sports Media Group, says the Cowboys are among a handful of "national-appeal teams" that draw huge TV ratings no matter what market they're broadcast in. The Cowboys also were helped in the study by the massive amount of traffic their website draws—nearly 50% more monthly unique visitors than the second-place Steelers.

On the other end of the spectrum, five of the eight teams in the NFL's two West divisions are in the bottom 10 of the overall rankings. This includes the St. Louis Rams, who, on top of averaging an embarrassing two wins per year over the past three seasons, finished last in this report. They have the worst mark in two of the categories and were in the bottom six in the others.

"When you've won as much as we have recently, it's not surprising," says Kevin Demoff, the Rams' executive vice president of football operations and chief operating officer. But it's not as though the Rams are incapable of being popular. When they reached multiple Super Bowls a decade ago, "everybody in the city loved us," says Hall of Fame-caliber running back Marshall Faulk, who played on those teams.

The Nielsen report uses one year of data, but separate research from the past two decades has shown similar results. Harris Interactive, a New York market-research firm, has been asking respondents to name their favorite NFL team annually since 1992. The Cowboys came out No. 1 on 11 occasions in that poll and were never lower than No. 4. The Rams, since they moved to St. Louis in 1995, were in the bottom five on five occasions. The only teams that fared worse than the Rams were the Bengals and the Jaguars. The Tampa Bay Buccaneers finished next-to-last in the Nielsen study.

The Jaguars declined to comment. A spokesman for the Bengals said the team would likely perform better in these rankings next year, and a Bucs spokesman said the faltering Tampa economy likely played a large role in recent struggles to attract fans.

The study shows a winning tradition doesn't guarantee a large fan base. Two of the NFL's more successful and iconic franchises, the Oakland Raiders and San Francisco 49ers, finished near the bottom of the rankings despite owning a combined eight Super Bowl titles (representatives for the teams couldn't be reached for comment).

Despite the healthy rankings for the Packers and the Saints (No. 9), the study suggests being in a smaller media market presents some challenges. Five of the bottom 10 teams hail from Charlotte, Kansas City, Jacksonville, Tampa and St. Louis.

That said, it's not clear what to say about the New York Jets. (They finished No. 18).

Write to David Biderman at David.Biderman@wsj.com