A few things with the games:
1) The "main quest" in the game is to complete the pokedex, getting the badges and beating the elite four is more of a "side quest", but when you beat the elite four everything happens(new areas open,some legendaries can be found, end credits, new item,...) but nothing exciting happens when you complete the pokedex.
b) This is more of a personal thing, but when I was 5 and was playing Yellow for the first time, I didn't notice the exit from the Viridian Forest. It blended in too well.
III) I feel bad for the NPC trainers who have to start in towns surrounded by high-level pokemon.