off the top of my head i can think of: neopets, tamagotchi, nintendogs, sims 2 pets, webkinz, chicken smoothie, aywas, subeta, howrse, flight rising, lioden, wolvden, the final outpost, the old PC petz games, and i also tried creatures recently. i would basically sign up for any random browser pet game i could find as a kid so i'm sure i have played more but those are the main ones i recall spending a decent amount of time with. lately i only actively play neopets and flight rising