Best game? Well there has been one game that I have remembered vividly since the PS1, every tiny detail and I could still play it today as well as I could then if not better.
The game was Monster Rancher, yes, it was a raising a pet type of game but it had it all for a PG game, you had your basic monster, you fed it, trained it, entered it in tournaments, combined it with other pets and so on but the one part that made it the best game for me as a kid was that your monster died of old age. I don't mean the dying was good at all but it was very.. emotional, I was only young but I remember pumping hours and days into a single monster and I'll admit to getting very attached to it, there was one in particular, I can't remember what I named it but it looked like this, mine was the green dinosaur/dragon-like one.
I never knew there was 2,3 and 4, only ever got to play the first so that has saddened me now. Anyway for me this is/was the best game for how emotionally involved I got as a child into it plus the overall gameplay still looks pretty solid to me today really.