Yeah, the only generation in which I like all Pokémon is the first, in the second I like them all but a few (Houndour/Houndoom and some other abominations whose name shouldn't be spoken of, as that will lure them out of their filthy den), the third I have a hard time liking most of them (The starters are alright, with the grass evolutions line being my favourite in my game, Aggron, Zangoose (is a borderline), Corpish/Crawdaunt, Delcatty (NOT Skitty), Keckleon and Relincanth being alright) and the D/P versions where I find most but a few pokémon appealing as well (Probopass, Magnezone, Tangela's evolution, Hippowdon, Gliscor and Drapion are some abominations to mention, but to forget as soon s they're heard).
But you do agree that drawing 400+ pokémon and still keeping up with the same quality is a hard task, right? Just tracing all those is a hard enough task, so how hard wouldn't it be to actually draw and invent them from scratch? Just look at all rubbish pokémon from many hacks that look abominable all of them.
Who knows, maybe Ken Sugimori had a lucky streak when drawing the first generation- but still we are the most attached to the ones we grew up with.