The correct answer is: they are celebrated every 2 years.
The Pan American Games are held every four years, but they are staggered with the Olympic Games, which occur every four years as well. However, in terms of the frequency within a certain time frame, the Pan American Games might seem to occur more frequently for specific regions or contexts compared to the Olympics.
To clarify, the other options are not accurate representations of the difference between the two events, such as the claim that only Cuba can host the Pan American Games, which is incorrect as multiple countries in the Americas can host the events. The Pan Am Games do feature some unique sports, but the significant main difference is the frequency of their occurrence, which is more aligned with the general statement of their every two-year gap within the cycle of the Olympics.