There are some Pokemon that appear in almost every game and generation regional dex and some that only appear in one or two. Are you tired of seeing the same mons over and over again while the other ones are kicked into post game?

Common ones: Zubat, Machop, Abra, Tentacool, Geodude, Pikachu, Gastly, Wingull, Staryu, Koffing, Rhyhorn Sandshrew, Psyduck, Magnemite, Goldeen, Magikarp, Eevee, Marill, Ralts, Riolu, Nosepass, Aron,Meditite, Roselia,

Rare ones: Mankey, Tyrouge, Drowzee, Paras, Venonat, Meowth, Ponyta, Seel, Krabby, Kangaskhan, Porygon, Ledyba, Spinarak, Natu, Suddowoodo, Sunkern, Pineco, Girafarig, Snubbull, Qwilfish, Teddiursa, Phanpy, Stantler, Seedot,Slakoth,Shroomish, Numel, Spinda, Cacnea, Corphish, Tropius, Kricketot, Cherubi, Shellos, Glameow, Bronzor, Finneon.

I listed only first evos.