>Game starts almost straight away with a succinct objective
>Non-linear - you can literally go 1>2>6>5>7>4>3>8 for badges if you want
>Genuine challenge in the Safari Zone, Game Corner and not using Great/Ultra/Master Balls when completing the Pokedex
>Top tier music with a unique style (suspense and uncertainty used specifically as a thematic approach)
>100% playthrough is actually doable with having to be 100% autistic
>Top tier dialogue (e.g. Blue's "Do you know what that means? I'll tell you! I am the most powerful trainer in the world!" followed by epic music so you're like oh shit boys here we go then)
>On the topic of dialogue, there's no political-correctness-gone-mad bullshit censorship
>Fun glitches to mess around with

The genwunner thing gets bandied about, but we all know that both it and Gen II (which most of the above also applies to) are easily the most vibrant and artistically valid of the entire series. It's pretty much objective at this point.

tl;dr Gen I/II thread.