Gen One has a large amount of favorites simply because of the sheer number of simple, but iconic designs. This was the only generation where I really got into the anime for, combined with the popularity of pokemon go caused me to fall in love with so many pokemon from this gen, despite having never finished a gen one game.
Mew: A simple but amazing Pokemon that I love mainly because of the large mysteries surrounding it, and it's appearance in the first movie. Charmander Line: A common favorite that just happens to be my favorite of the gen one starters. I'm a big fan of the entire starter trio, but a giant firebreathing dragon really appeals to me. Raticate: Being a rodent lover and having been a rat owner at one point, raticate's doofy rat-like appearance really sold me. Pikachu Line: Sandshrew Line: Jigglypuff Line: Growlithe Line: Haunter: Chansey: Lapras: Eevee: Vaporeon: Kabutops: Dratini Line: Mewtwo: