The Pikachu Family

Here he is, folks, the golden calf of the Pokemon brand. Pikachu was chosen relatively last-minute to be the "mascot" monster of the series, and twenty years later, the world generally ranges from marginally indifferent to positively sick of the yellow rodent. This is an inevitability for any single character saturating the market to such an extent, so it's hardly pika's fault, and they honestly made a pretty good choice here. Pikachu is simple to draw, easy to recognize at a glance, just cute enough - especially in these blobbier Sugimori drawings - and just slightly weirder than a normal, mundane animal thanks to its cartoon lightning-bolt tail and electrical powers.

It really does feel like the most "marketable" critter in the first generation; a safe bet to gamble so much brand recognition on, and one that ultimately paid off.
Raichu, of course, is a lot cooler looking than Pikachu, especially with its more whip-ike tail, but Pikachu's status as the face of the franchise has shoved its own bigger, stronger, final evolution into its shadow. That has to suck for Raichu, knowing you're objectively better in every measurable way but that some young punk is going to soak up all the attention instead. Poor Raichu. Raichu was even portrayed as kind of a jerkoff in the anime. Pikachu didn't even want to ever be a Raichu.
With Pikachu merchandise flying off the shelves world-wide, it was only logical that they take things a step further and introduce a baby Pikachu in the second generation, known as Pichu, which really is about thirty million degrees more darling. Pikachu looks like a big steaming pile of barf next to Pichu. The world was not ready for a tinier, squeakier Pikachu, and it still hasn't fully recovered from Pichu's reign of terror.

Pikachu's overexposure puts it fairly low on most favorite pokemon lists, but a lightning-hurling chinchilla-like rodent isn't a bad concept at all, and Pikachu fills its role as series mascot quite well. Kudos to you if it's still one of your favorites on its own merits, and even more Kudos if you're a Raichu devotee. I'm gonna give the 'chu three and a half out of five.