come to think of it, I've never really used Alakazam or Gengar in any Pokémon game outside of some showdown. THough, Golem was an MVP on my first reborn team and I used a Machamp in OrAs
I wish I could use Gengar more often but I just don't have friends, so it's restricted to fangames, and the OG ghost is (rightfully) often unavailable early on.
I used alakazam in two different Reborn playthroughs and it was a total beast each time. It's a glass cannon with some cool support potential as well. Probably among the the most mage-ish pokemon out there.