Piplup is the all-time best pokemans.
Well, it's because I used to work at a GameStop, that's why
But to be serious for a second, I had a falling out with the Pokemon games for a while and when Diamond and Pearl came out (while I was working at a GameStop, that part was true) I found myself falling back in love with the game. It was almost like I was experiencing the whole series for the first time. It was great. I lost hours and hours playing that game and if I could find my Nintendo DS, I'm pretty sure I'd be playing it right now. So, maybe I like him for more sentimental reasons instead of scientific.
[note: Piplup is scientifically better than Mew]
Thanks@VinMcCarthy for another great video game challenge, I can't wait for the next one.