Pretty straight forward:
In Gen I, what was the most common type? In Gen II, what was the most common type? In Gen III, what was the most common type? In Gen IV, what was the most common type? In Gen V, what was the most common type?
\m/o_o\m/
Gen I has poison with 35 poison types Gen II has normal with 22 normal types Gen III has water with 28 water types Gen IV has normal with 17 normal types Gen V has bug with 18 bug types
Please know this I did not count different forms of pokemon