This is the epitome of comparing apples to oranges. The Super Bowl is a single-day television event, largely isolated to just the United States. The Winter Olympics, while international, doesn't have the same kind of viewership that the Summer Olympics has, possibly because it largely excludes countries that don't participate in winter sports. The Winter Olympics also has the advantage of putting up large numbers because it is televised on multiple stations that showcase multiple events over the course of a couple weeks.
The World Cup trumps even the Olympics. It is a month-long event that takes place in the summer and televises the world's most popular game to an international audience. Corporate sponsorships are priced ~$75 million per sponsorship. That's nearly 20 times the cost of a Super Bowl ad, BUT this includes a lot of bonus spots and a confirmed number of spots that eclipses 400. This puts increased pressure on agencies and corporations to keep their message fresh because no one wants to be diluted with the same commercial over 400 times for a month.
The Olympics offers more competitive rates over a sustained period, but ratings will likely diminish based on time of day, event, and so forth…Figure skating may not appeal to a younger audience, whereas snowboard superpipe may not appeal to an old crowd.
The trick to determining whether or not to advertise during one of these highly visible sporting events is to do some thorough cost analysis and opportunity cost analysis and decide which suits your target demographic best. Will the impression you get with a Super Bowl ad give you the frequency you want? Will the frequency you get with a World Cup or Olympics ad reach the number of people you want it to reach (think Croatia vs Cameroon in the WC or Curling for the Olympics)?
Regardless of what happens, the CPM will continue to rise and so will the price for a single spot (as high as $10 million/ 30 seconds for the Super Bowl by 2040). Why does this happen? It's not just because of the VOLUME of people reached, but the quality of ads increases on the world's biggest stages. During the Super Bowl, people don't turn the channel, the viewership of advertisements actually EXCEEDS that of the game itself! Exciting times indeed….