It seems to me like Pikachu starts over every season, or something.
I mean, if the anime actually went by levels, and exact stats as the games do, Pikachu would be well to level 100 right now, and would have little or no chance at all to lose as much as it does. Not that it sucks, or anything, but really.. it lost to Shinji's Pokemon. Shinji's Sinnoh 'I've just caught them, so lets test their power' Pokemon. That wouldn't ever happen.. if the anime went by levels, and Pikachu really was close-to, or at 100... Shinji would've been owned. >>; The same can be said for most of the Gym Leaders, and possibly Frontier Brains.
I don't care how good at battling Shinji is, if his Pokemon were at those weak levels, he couldn't have won.
Either that or, the writers just disable Pikachu from leveling passed level 30, to make it so it can still be defeated.. even by the weaker gym leaders. oO;
Granted.. no one has to agree with any of this.
But theres my one cent worth of an opinion..