This Pokemon has a spiral horn and I see some detail on the fin on its back, and I think this was removed later.
Looks like scales, but these were also removed, at least from the back sprite.
There is a pattern on the body that was removed.
This early sprite is also very detailed.
I looked for some improved details, and see it's also the other way around.
The new sprite has another pattern on its body and the wing pattern look more than just highlights.
I expect that a newer game should have at least the same details as the games before, and expectations play a big role in how you judge the game. I find it easier to see when something is missing than when something is added, because you always have an older version to compare to. My guess about the removed patterns on some of the Pokemon is that the spriters saw no need in these details because the new colours could make up for it. My other guess is that details disappeared with Yellow version when the sprites were supposed to look more cartoonish. About the colours, the Super GB colours are not better in that sense of the word, it's just my own opinion, I think the colours chosen for the DS Pokemon games are far too bright and intense.