Floatzel - No surprise I put my favorite Pokemon here, Buizel is somewhat popular, but it's evolution is extremely overlooked. It has a cool design, great stats, and a great moveset, and yet it's barely mentioned by people in comparison to it's pre-evo. One person told me that it's not popular due to not that many appearances in the anime and manga (which I agree with), as well as him complaining that it's "just a bigger Buizel", when really, why is it a problem just for being "a bigger Buizel", Arcanine is just a bigger Growlithe, Muk is just a bigger Grimer, Dugtrio is just three Diglett, Magneton is just three Magnemite, and those were all Gen 1 Pokemon I mentioned. Why should Floatzel be ignored for that reason?

Mienshao - A Pokemon that's looked upon probably even LESS than Floatzel, great stats, great moves (it even learns Aura Sphere), and a unique design, but is almost barely mentioned in comparison to other Gen 5 Pokemon.

Watchog - Ridiculed for being both allegedly ugly and being a regional rodent, I think it's cute to be honest, and it learns a few good moves actually, and yet it gets ridiculed by people for being a rodent.

Manectric - One of the best concepts for an Electric type with a variety of good moves, and it gets ignored in favor of Ampharos and Luxray.

Ninetales - One of the first Pokemon I ever loved. Fox based Pokemon are almost always the most popular Pokemon, but in comparison to other fox Pokemon like Eevee, Zoroark, and most recently Braixen, Ninetales is barely even mentioned anymore, and just like Floatzel, Ninetales isn't as popular as it's previous form Vulpix.

Druddigon - Looked over in comparison to other Dragon types for some reason, probably due to being standalone.

Overrated:

Pikachu - Obvious reason is obvious

Eevee and all of it's evolutions (Umbreon and Espeon most especially) - This is a Pokemon I am anymore getting sick of seeing, it's in almost every fan-fic and fan-comic (if it's PMD, it's almost ALWAYS the main character), you go on DeviantART and almost every other Pokemon pic is an Eeveelution one. To me, the only reason people like Eevee is because it's a cutesy fluffy Pokemon, and cutesy fluffy Pokemon are always the most appealing to people. It's also the most unoriginal choice for fan characters, there are over 700 Pokemon at this point, and they keep always going to these ones, get original people...

Every Fire starter (except Tepig) - The Fire type starter (with the exception of Tepig because of the Fire/Fighting controversy) is ALWAYS the most popular of each generations starters, and not just a specific form, but the whole evolution line. The most popular is Charizard due to being one of the most recognizable Pokemon, followed by Blaziken for it's stats and moveset, and it seems like Fennekin is heading in the same direction, double points for it being a fox Pokemon.

Ampharos - Everyone seems to like this Pokemon for some reason, and I just don't get why, I never really found it that appealing.

Luxray - Remember what I said about Manectric? This Pokemon is so common in fanart and peoples teams it's unreal at this point.

Lucario - Do I REALLY need to explain this one? It got it's own movie, it was in Brawl, and now it has a Mega Evolution that's becoming more popular than the Gen 6 Pokemon simply for being Lucario, and even the most popular Gen 6 Pokemon (which at this point is now Braixen) cannot hold the torch in its tail up to it.

Zoroark - Same reason as Lucario.

All Dragon types except Druddigon - Enough said, ESPECIALLY Garchomp, which is now worse since they gave it a Mega Evolution now...

Tyranitar and Metagross - Same reason as the Dragon types, and I just find Metagross ugly in my opinion.

Any Pokemon that has somehow spawned an internet meme - I'm looking at you Slowpoke, Magikarp, Mudkip, Bidoof, and Stunfisk