I looked through all the Kanto Pokémon and found several Pokémon with noticeable differences.
(left is Ruby/Sapphire, right is Emerald)
Wartortle is more purple in Emerald (no, that's not its shiny form):
![Wartortle](https://img.pokemondb.net/sprites/emerald/normal/wartortle.png)
The outline around Caterpie's feet blackens (credit to Scorby). The far-side eye and tail-tip are also a bit different:
![Caterpie](https://img.pokemondb.net/sprites/emerald/normal/caterpie.png)
Lickitung loses the smile:
![Lickitung](https://img.pokemondb.net/sprites/emerald/normal/lickitung.png)
Jynx's skin tone is slightly lighter:
![Jynx](https://img.pokemondb.net/sprites/emerald/normal/jynx.png)
Snorlax speaks for itself:
![Snorlax](https://img.pokemondb.net/sprites/emerald/normal/snorlax.png)
I found no major differences between any Gen 2 sprites.
Even though you said you don't need all of them, I'm going to go through it anyway because why not. Gen 3 will be added when I have a chance to look through them.