Sadly, people do often choose Pikachu over Raichu because of that stupid light ball, but other than that Pikachu isn't used much.
Eevee and any of its evolutions.
Ask anybody what is their favourite Normal, Fire, Water, Electric, Dark, Psychic, Ice, Grass or Fairy type. Count how many people answer with any of the following: Eevee, Flareon, Vaporeon, Jolteon, Umbreon, Espeon, Glaceon, Leafeon or Sylveon.
The Eeveelutions, while a nice way of introducing new evolution gimmicks, are usually laughably weak and outclassed, and the fanbase goes crazy of them. I'm convinced they're more overhyped than Charizard, and most of the people who dislike the 'zard for being overhyped usually like the Eeveelutions. It's a vicious cycle.
I think Mewtwo is overrated, people call it and it's Mega Y evolution OP and yet I've always found them to be rather easy to beat.
He's just a glass cannon if anything.
The Kanto starters (and their evolutions) and Pikachu.
I don't absolutely hate these Pokemon, though. I mean, for example, I had Pikachu/Raichu on both X and Y teams. The reason they can be overrated at times is because they seem to be the only Pokemon on any Pokemon shirts I've seen sold in various places.
There's other Pokemon that can be used on T-shirts than these four, folks!
Yeah, I can also agree that the Kanto starters are overrated (I mentioned Charizard before). They're all protected by thick layers of nostalgia and I really don't get what's so appealing about them.
Got a few more:
Blaziken: Again, like Charizard and Greninja, tons and tons of favouritism. The only thing it doesn't have is a black shiny colour, but just like those two, gets far more than the other two of its generation.
Aegislash: I honestly don't get what's so appealing about a possessed sword.
Garchomp: It's everywhere. Literally everywhere.
Froslass for those nasty Garchomps, buddy.
Anyways, I fully agree with your post. Do people even have some creativity nowadays? Must be kind of boring using the same Pokemon every time.