Ruby, Sapphire and Emerald all had the same sprites, which is pretty lazy of them (considering they also removed day&night and other features gen 2 introduced). Crystal had animations while R/S had static sprites. Untill Emerald came around we'd have animated sprites again, but not even it wasn't as good as Crystal's. Emerald's "animation" was just stretching the sprite horizontally/vertically, it looked piss poor and just lazy.
As far as the gen 3 sprites go, they look pretty boring and stale/bland. Partly the GBA saturation is to blame. The sprites really look like cardboard cutouts, gen 3 has the worst sprites in my opinion.
The Kanto Pokémon especially got shafted in R/S/E (look at poor Nidoking, he looks like he got sterilized), but that would be fixed in the remakes
