Charizard... I can totally see him flying around setting fires to every forest in the World and causing global warming to the Earth and starting a Pokémon apocalypse! He will finish what Mewtwo couldn't do and wipe out the Human race!!

Oh and Speaking of which, a Mewtwo game as well. Where he tries to take over the World Picky and the Brain style.

Magikarp with an everstone.

Eevee and the Eeveelutions.

ジガリーフｱクトル or known in the West as Jigglyfactor a Japanese game show singing contest... And Jigglypuff stars in the game for it.


$$$$$$$$$

Bidoof + Whack a mole

Pikachu with.... anything really :p

The Adventures of Dunsparce.
The game is about moving around, existing, and stuff.

Angry Hawlucha
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An Angry Birds/Pokemon crossover, with Hawlucha playing the role of the birds, and Spoink as the pigs, with other pokemon appearing in cameos, as bosses, etc, and a few other flying types also playable, including Emolga, Rufflet, Gligar, Delibird, Natu, Vullaby, and Noibat, complete with type effectiveness effects.

It would still be better than Hey You, Pikachu!

Eevee could. Like a Mega Man-esque title where you go through a level and at the end acquire a new Eevee-loution could be good to see.

Aside from that, Lucario could star in his own fighting game if you ask me. You know, like Bayonetta but less sexually provocative (or more I suppose for some people). Pokemon are great but they're mainly secondary characters, so you'd have to really construct a personality in order for something to work.