joshd1000.deviantart.com/gallery/5571072 This guy has most of the first gen drawn realistically, with scientifically plausible explanations. The thing I like most about his project is how he doesn't change the pokemon's design to much, he just makes it looks realistic.
He doesn't decide what real-world animal the pokemon looks most like and draws that animal with some of the pokemon's features, eg; making bulbasaur a frog with a bulb on it's back, he just drew a dinosaur-looking thing with the bulb.

Pic related, it's his Golduck.