I did something. Here are numbers for Pokemon I got for each gen:
Gen 1: 151
Gen 2: 100
Gen 3: 143
Gen 4: 134
Gen 5: 164
Gen 6: 125
In order to get these numbers, I added each gen's new native Pokemon, new cross-gen babies and evos, and new formes. In terms of formes, I didn't include any that were aesthetic only (including gender differences). I included both permanent formes and formes that only exist within a battle (Darmanitan, Castform, mega evolutions, etc). The only gender differences that were included were for Combee and Meowstic because they're not purely aesthetic. You can infer from this information what you want.
>Gen 1 - 151
151 native Pokemon
>Gen 2 - 100
83 native Pokemon
7 cross-gen babies
10 cross-gen evolutions
>Gen 3 - 143
133 native Pokemon
6 native formes (Castform, Deoxys)
2 cross-gen formes (Unown)
2 cross-gen babies
>Gen 4 - 134
79 native Pokemon
27 native formes (Wormadam, Combee, Cherrim, Rotom, Giratina, Shaymin, Arceus)
7 cross-gen babies
21 cross-gen evolutions
>Gen 5 - 164
156 native Pokemon
8 native formes (Basculin, Darmanitan, Tornadus, Thundurus, Landorus, Kyurem, Meloetta)
>Gen 6 - 125
71 native Pokemon
3 native formes (Meowstic, Aegislash, Hoopa)
1 native mega evolution
1 cross-gen evolution
47 cross-gen mega evolutions
2 cross-gen primal reversions
