I love looking at the early stages of a a creative work I've experienced in its finalized form. You get a glimpse of what-almost-was, what-could-have-been, and sometimes the thank-god-that-didn't-happen.
Bulbapedia has a fascinating page on prototype Pokemon and prototype trainers, as well as some Pokemon that just plain never made it into a Pokemon game. (Yet?)
Maybe you'll find these more pleasing than the actual Pokémon that Gamefreak created—that is, if you're one of those crazy people who thinks Pokemon designs are getting worse.
Regardless, there's a bunch more at Bulbapedia that you should check out, including Slaking, Tyranitar and others. We've also covered a few early designs here.
Prototype Pokémon and characters [Bulbapedia]