Anatomically speaking, there's just no way a living organism could retain the traits that make Pokemon look like Pokemon. Most of what makes them what they are, are the anime depictions of them. Realistically, everything from eye form to body shape would be altered in a real-life setting. Furthermore, we can't even tell what half of the Pokemon are made of - skin? feathers? fur?
Take Milotic for example, since it was mentioned. The picture isn't particularly nasty looking...it just has teeth, something that Milotic would mostly likely have.
Mr. Mime - Would you really think a small clown-looking figure with cartoon eyes would be a realistic approach? We don't know if it has hair, so the artists interpretation is that they're actually horn-like appendages. With a Pokemon like that, it's very difficult to imagine a realized version of it. I guess this is why they're cartoons and not real, though, right?
Like I said, I feel like in order for Pokemon to translate to realistic figures they would be drastically altered in appearance and come out extremely alien, at best.