It was a sensation when it arrived in the US right at the turn of the century. Today, Who Wants to be a Millionaire? is the 3rd longest running syndicated game show on the air, behind, of course, Wheel of Fortune and Jeopardy!, which have been around much longer.
Millionaire began as a primetime entity, airing almost on a nightly basis at one point, on ABC, which overmilked the ratings-boosting phenomenon a little too quickly. Talk show icon Regis Philbin hosted the ABC version during its 3 year run (1999-2002), but due to his daytime talk show, couldn't continue when the series moved to syndication in September 2002.
At that point, Meredith Viera (The View) was tapped to succeed Philbin. Having played the game certainly helped. During her run, Viera began a 4 year stint on NBC's Today (2007-11), concurrent with her Millionaire duties. After 11 seasons, Viera stepped down, and actor-comic Cedric the Entertainer (The Soul Man) took over. However, Cedric lasted one season, and was replaced by Terry Crews ("The Expendables", Brooklyn Nine-Nine) this season. It was reported earlier this week that Crews is stepping aside for The Bachelor's Chris Harrison this fall.
The game itself is rather simple, though it was tweaked 5 years ago for no other reason than to try to freshen the franchise.
Let's take a trip back in time with Regis, dating back to March 2001.
I haven't seen it since it went into syndication, but the above video represents what I remember.