Alright, let get some—sort of—science in this thread. There's this site called "Sporcle.com" where you can test your knowledge of subjects ranging from pop culture to science. Of course there's a Pokémon quiz where you have to name all Pokémon of a specific generation. I've only done the Gen I quiz (
link), which has had over 1.5 million participants, making it by far the most popular quiz in the gaming category. If that's not a giant sample size then I don't know what is.
Anyhow, the least forgotten Pokémon is obviously Pikachu with 93.8% and the most forgotten Pokémon in this quiz is
Exeggcutor (Points to Teal) with a pitiful 33.6%, which means barely over a third of all participants remember him, and remember that a lot of participants probably just wrote down the Pokérap. Exeggcutor is followed quite obviously by Exeggcute at 33.8%, Lickitung at 35.8%, Kingler at 37.8% and krabby at 39.2%.
The top 20 continues as follows: Shellder, Dodrio, Pinsir, Parasect (WHAT'S WRONG WITH YOU PEOPLE?!), Cloyster, Farfetch'd, Tangela, Seadra, Drowzee, Cubone, Slowbro, Paras, Rhyhorn, Porygon and lastly Hypno.
So that's it, a lot of really awesome Pokémon (like for example Hypno, Cloyster, Slowbro, PARASECT NO SERIOUSLY HOW IN THE WORLD, WHAT IS WRONG WITH ALL OF YOU????, and Tangela) seem to not be quite as memorable.
If you want to see the rest of the percentages or the percentages for the other generations, simply do the quiz yourself; the results page shows all the percentages.