Hamburger consumption started at 80 grams in the year of 1970 and experienced an constant increasing trend ever since, and the trend has even become sharper since 1983, which ensured its dominant position in all 3 fast foods.
Pizza, running a similar tendency as that of hamburger consumption, increased from 30 grams in 1970 to 285 grams in 1990, which was almost 100 folds of what is was in 1970. In spite of the drastic increase, pizza never caught up with hamburger in popularity, and the difference between the two is actually growing.
Fish and chips, though starting at a much higher level of consumption at 300 grams in 1970, fell to 200 grams in 1984. Despite the fact that it started to climb after that, it remained the least popular fast food due to its slow recovery.
In conclusion, hamburgers are on their way to become the hotties of the fast food family.