A few weeks ago a Twitter user made a poll asking people to pick any and all Pokemon they like for each region and I thought the results were interesting. Note that this isn't about which Pokemon is the most popular in their generation, but which ones are the most widely liked.
I'll post the Top 3 most and least liked Pokemon for convenience:
>Kanto
Bulbasaur, Arcanine, Gengar - Most
Raticate, Drowzee, Kakuna/Goldeen (tie) - Least
>Johto
Umbreon, Espeon, Ampharos
Igglybuff, Granbull, Snubbull
>Hoenn
Metagross, Flygon/Gardevoir, Mudkip
Illumine, Volbeat, Cascoon/Luvdisc
>Sinnoh
Garchomp, Empoleon, Luxrai (Lucario is 4th)
Burmy, Wormadam, Bibarel
>Unova
Chandelure, Krookodile, Volcarona/Galvantula
Patrat, Watchog, Basculin
>Kalos
Aegislash, Greninja, Noivern
Aromatisse, Binacle, Bergmite
>Alola
Mimikyu, Rowlet, Primarina/Decidueye (tie)
Gumshoos, Yungoos, Trumbeak

If you want to see the full results, I posted them on this Imgur link
>https://imgur.com/a/sfRWjRe
or here
>https://linkto.run/r/8I36502E
>https://linkto.run/r/QH2SUPBI
>https://linkto.run/r/TQKDA048
>https://linkto.run/r/UI5RZ3SN
>https://linkto.run/r/UT4GDIRG
>https://linkto.run/r/7Y30XB2S
>https://linkto.run/r/34HCF07B