basic, I know, but I do have quite a soft spot for gengar..
when a pokemon is popular. it is usually because it is good.
i think i am in the minority here but i genuinely find gengar really scary. i know she is a silly little guy who just wants to play and i appreciate that she is getting merch for Being Cute (WHICH SHE IS) but the idea of an entity in the darkness that has glowing red eyes and is always smiling a cheshire grin terrifies me. and i think she should get her flowers for that. she is cute and silly but she is also genuinely a bit unnerving!!! and that is exactly what a ghost type should be.
i, of course, love the doppelgengar theory and 100% believe it to have been the intention all along (its name is a play on doppleganger, amongst everything else) and really love when pokemon come in Pairs, and the retroactive fairy typing on clefable makes their normal/ghost and fairy/poison ouroborus SO delicious. also they should make out.
gengar got one of the better journeys episodes AND it was even a sickfic (in japanese, they censored it in america)
all gengar were human once. terrifying. gengar is ken sugimori's fave pokemon because she's easy to draw. it has a unique gigantamax animation. its evolutionary line depicts a story about a ghost breaching the veil of living and dead to return to the physical world.
the pokedex entries come alola all just snapped and were like "you know what? nah. let's make this thing terrifying again."
(send me your fave / least fave poison type and i will tell you everything i love about it)