Apart from Gary's face looking god damn terrifying, the animation was awesome - very smooth and it was cool seeing Pokemon characters in this style. I think someone's already mentioned this, but the Pokemon themselves are a little smaller than they ought to be, but that's not a huge deal.
Also, I completely understand wanting to use Ash's and Gary's voices from the anime in this, but - and maybe I'm the only one that thinks this - combined with the style of animation it's just pretty awkward. It doesn't fit at all. Maybe I'm the only guy with a problem on that front, but it's just how it came across to me. I'd invest some time in finding decent voice actors (they're all over the internet) who can do more fitting voices for it.
Overall, though, very well done! Looking forward to seeing the rest.