Contestant Doug Van Gund with Regis Philbin on 'Who Wants to Be a Millionaire' in 1999.(Photo By Getty Images)
CNN  — 

Twenty years ago, “Who Wants to Be a Millionaire” took primetime by storm, during what was traditionally a quiet time in the month before the start of the fall TV season. While the quiz show recently ended its run, its impact continues to ripple through television, having opened the floodgates to all forms of unscripted projects.

Based on a British program and hosted by Regis Philbin, “Millionaire” made its debut on Aug. 16, 1999 as what amounted to summer filler. It almost immediately caught on, prompting ABC to bring it back as a four-night-a-week franchise that drew nearly 30 million viewers per episode at its peak, promptly elevating the network to first place in the ratings.

Like an asteroid, that huge glow shot across the sky and quickly faded – or at least, came back down to Earth. But the impact lingered, as networks were suddenly more receptive to what were dubbed alternative programming genres, especially in the form of game or competition shows.

CBS followed the next summer with two more imported European concepts, “Survivor” and “Big Brother,” which offered the next permutation on “game shows,” in that case wedded with the formula of a reality-based soap opera. Suddenly, what came to be known as “reality TV” was off to the races.

“Millionaire” demonstrated that inexpensive programming – at least, relative to sitcoms and dramas – that had largely been relegated to the daytime hours could not only work but dominate primetime.

Contestant Bernie Cullen (left) with Regis Philbin in a 2001 episode of 'Who Wants to Be a Millionaire.' (Photo by Maria Melin/Walt Disney Television via Getty Images)

At the time, TV executives sounded ambivalent about the trend. Some lamented what they saw as low-brow, cut-rate programming, while others merely saw it as the medium returning to the quiz shows that played on networks during TV’s infancy.

“I don’t think anything dies,” former ABC Entertainment chief Stu Bloomberg said back in 2000, noting that the nice thing “Millionaire” did was “show that people will accept [different formats] in prime time again. I never understood it when people said, ‘That doesn’t feel like a prime-time show.’ “

As is so often the case, though, “Millionaire’s” success brought with it unintended consequences. As unscripted TV occupied more shelf-space on the major networks, cable channels like FX filled the void with “The Shield” and “Nip/Tuck,” followed by AMC’s “Mad Men” and “Breaking Bad.”

The increase in networks and eventually streaming services using original scripted shows to brand themselves ratcheted up the competitive pressure, and eventually helped squeeze broadcasters almost entirely out of the conversation in terms of the prestige TV/award-show circuit.

Contestant John Joh John Carpenter (kissing his wife, Debbie) became the first $1 million dollar winner on the show in 1999. (Photo by Maria Melin/Walt Disney Television via Getty Images)

On “Millionaire’s” 15th anniversary, The Atlantic published an article arguing that the program’s most enduring legacy stemmed from the proliferation of reality-competition shows, which featured the big money and dramatic tropes in a slightly different package. To that extent, the quiz show “led to dramatic change in how primetime TV is developed.”

Granted, all of that might have transpired, one way or another, without “Who Wants to Be a Millionaire,” given the combination of increased competition and fragmented audiences inspiring networks to balance production costs. As for the question of whether the series lit the match that triggered the change, the likelihood of that being the right “final answer” is considerably better than a one-in-four chance.