Rank the generations aesthetically. As in, what looks best to you, especially for the time it came out and power of the hardware?
IMO:
2 > 4 > 1 > 3 = 5 > 7 > 6 > 8
I would probably rate 7 and maybe 6 higher than 3 and 5 if everything wasn't so desaturated and models were a bit more dynamic in posing in-battle.
5 has really high quality pixel art outside of the tweening animations but I don't think it blends well with the 3D models and it feels a little bit too blue in tone outside of summer.
3's my favourite gen but it's definitely my least-favourite of the 2D games artstyle wise. I think nothing but shinies and specific battle sprites really pop well, which is ironic because most GBA games were oversaturated. Not to mention I think the lack of day/night visuals really hurts it, would've been cool to explore the island/ocean section of the region at night. Tilesets for FR/LG are especially bland, although that might be overexposure from bad 00s ROMhacks when I was younger.
Gen 2 and 4 both look really crisp, although I think considering it came out in the DS era Gen 4 could've had a little less overly grid-based tilesets.