The New York Giants’ thrilling win over New England was the most-watched Super Bowl ever with 97.5 million viewers, a total that is second only to the “M-A-S-H” finale audience, Nielsen Media Research said today.

The game eclipsed the previous Super Bowl record of 94.08 million, set when Dallas defeated Pittsburgh in 1996. The final “M-A-S-H” episode, which drew 106 million viewers in 1983, is the only other show in American broadcast history watched by more people.

Yesterday’s game had almost all the ingredients Fox could have hoped for: a tight contest with an exciting finish involving a team that was attempting to make history as the NFL’s first unbeaten team since 1972.

But the Giants ended New England’s bid for perfection, 17-14. Throughout the game, the teams were never separated by more than a touchdown.

Giants quarterback Eli Manning, who was to appear on David Letterman’s “Late Show” today, also won bragging rights over his brother: Last year’s win by Peyton Manning’s Indianapolis Colts was seen by 93.2 million people, now the third most popular Super Bowl.

Fox, a division of News Corp., charged $2.7 million for 30 seconds of advertising time on the game.

An eye-popping 81% of all TV sets on in the Boston area yesterday were tuned in to the game. In New York, the audience share was 67%.

The audience peaked between 9:30 and 10 p.m. — the fourth quarter — with 105.7 million people watching, Nielsen said.

There were signs even before gametime that Fox could be headed for a record. The opportunity for a team to make history with football’s first 19-0 record was a powerful draw. The Giants and Patriots also had a tight contest in late December that drew strong ratings.

The Giants’ underdog run had also captivated the nation’s largest media market, making up for the only potential weakness in the event as a drawing card: the lack of geographical diversity in the competing teams.

There were past Super Bowl games with higher ratings, topped by the 1982 game between San Francisco and Cincinnati (49.1 rating, 73 share). That indicates that a larger percentage of homes with televisions were watching the game. But since the American population has increased, along with the number of people with TVs, the actual number of people watching this year was higher.

The Giants-Patriots game’s actual rating (43.3 rating, 65 share) was the highest for any Super Bowl since 1997. That means 43% of the nation’s TV sets were tuned in to the game, and 65% of the TV sets that were turned on were watching football.