Route 228 lists 14 Pokémon across 12 encounter methods (grass (morning, emerald in the gba slot / firered in the gba slot / ruby in the gba slot / sapphire in the gba slot), grass (morning, leafgreen in the gba slot), grass (night, emerald in the gba slot / firered in the gba slot / ruby in the gba slot / sapphire in the gba slot), grass (night, leafgreen in the gba slot), and more), between level 3 and 55. 7 of them are on no other route's wild tables in this guide: Dugtrio, Cacturne, Hippowdon, Diglett, Cacnea, Sandslash, Beldum.
Route 228 in other guides
The same area in other ROM hacks on this site. Each one has its own encounter table.