Okay, this is the interesting thing about the Japanese, that's backstory. I don't think Pikachu was the first ever poke'mon they discovered (or created), I'm sure they found a bunch at once and started to study and take them in. Squirtle, Charmander, and Bulbasaur are all starter poke'mon because they're strong enough and also probably one of the easies poke'mon to master. Pikachu on the other hand is a stubborn poke'mon that isn't easy to master, and doesn't evolve on it's own like the other three. A trainer could keep a pikachu if it wanted and never have it evolve. (what Ash does in the anime) Seeing as how I'm a writer and all, sometimes what you want to be popular doesn't end up being the favorite. Other times, it's just the way it turns out because of the story itself. While the starter Poke'mon are cool, they aren't the coolest. So naturally the attenton wll be given to whoever appeals the most. I personally like Snorlax because along with my Starter Poke'mon he was a monsterin battle. I could take on the big 4 with my Snorlax alone. Yes, the anime had something to do with popularity, it played a part but because Poke'mon started off as a game first.
The "No anime" rule doesn't apply to Poke'mon and others, Sonic had anime, but started as a game. Same goes for Mario. There was an FZero anime, and yes, C. Falcon was in it. I won't bring up the Zelda anime....*shudders*. Fire Emblem, that anime followed Marth. Mewtwo was in the anime, as well as Jiggs. I'm sure Jiggs made it in popularity probably because of the anime....same as Mewtwo. ('cuz they weren't much use to me in the game. That's jut me though.)
I dunno, that' how I see the situation. Take it as you will. *nods* If I happen to have offended anyone, I apologize.