I like the ones that change a lot. I don't like when the shinies just look slightly lighter or darker than the regular one, beacuse it is hard to notice any difference.
The old way they did shinies was kinda archaic. It just went to the next palette, and the palettes were sorted in such a way that the shinies looked good. That's also why some shinies were the same, like Ditto and Mew.
With X & Y they got a bit more creative because now they have to texture the Pokemon, so it doesn't matter if they use simple color swaps or more elaborate recolors, the filesize is gonna be pretty much the same for the shiny texture anyway.
My list:
Rapidash, Gastly, Starmie, Dragonair, Azumarill, Umbreon, Murkrow, Slugma, Entei, Poochyena & Mightyena, Mega Gardevoir, Mega Mawile, Camerupt, Milotic, Luvdisc, Metagross, Regirock, Rayquaza, Shinx line, Spiritomb, Giratina Origin Forme, Serperior, Krokorok & Krookodile, Zoroark, Chandelure, Axew & Haxorus, Larvesta, Pumpkaboo, Yveltal, Zygarde, Diancie