I’m wondering what, in your opinion, is the best Pokémon game. Specifically not your favourite, but the one you would show to a complete newcomer to show what the mainline series is at its best.
My personal thought would be either Emerald or HG/SS, but I admittedly haven’t kept up with the series so much after Black and White 1, which I disliked the designs for and found too slow and hand-holdy.


For every single gym, there is an area where you can catch a Pokémon to counter it nearby. Very often you encounter a trainer who shows you a new Pokémon, and then it is available on thr next route.
With older gens you might not have all of the great improvements the series has made over time. Physical/special split, abilities, held items, color, multiple bag pockets, etc. Big Stadium and Small Court are available early as a source of exp and money farming that scales. The battle subway is great. The experience curve was re-worked and is much better. The games run and move a lot faster than Gen 4 and anything that came later.
The only downside is that, as DS games, it is annoying to have to emulate the 2nd screen and touch it occasionally. These games use that screen less than most DS games though.