Things I've never seen in the wild

I just caught my first larvitar a few days ago so I feel your pain.

As for never seen in the wild Blastoise, Venasuar, Machamp, Nidoking, Wheezing, Muk, Dragonite, Aerodactyl, Porygon, Omastar, Kabutops.

My main method of adding to the Pokedex has been hatching eggs and occasional rare find

Never seen any of these in the wild: Charizard, Raichu, Sandslash, Ninetales, Poliwrath, Golem, Rapidash, Magneton, Dodrio, Muk, Electrode, Exeggutor, Hitmonlee, Gyarados, Jolteon, Flareon, Porygon, Omastar, Kabutops, Aerodactyl. Yet I've encountered 10 wild Dragonites. Strange.

in gen1 i saw all pokemon on wild that can be encounter. in gen 2 i didnt see only tyranitar (last evolution) and wild blissey. The rest i encounter at least one time if i remember
(lvl 35.8 22k catches)

edit: i forgot about Unown - didnt see him aswel

Ooh, cool exercise!

My Gen1 wild no-shows are Raichu, Sandslash, Poliwrath, Machamp, Golem, Magneton, Dewgong, Muk, Cloyster, Electrode, Hitmonlee, Hitmontop, Rhydon, Chansey, Jynx, Vaporeon, Jolteon, Porygon, Omastar, Kabuto, and Aerodactyl. I have them all, but no wild seen/catch.

I'm L35.5 with 15,621 catches.

I'm same level as you and similar catches (14600). Live in a water biome but travel to a desert biome every so often. Have never seen a wild Gyarados, Dragonite, Alakazam, Aerodactyl, Exeggutor and Tangela (not even on sightings). Only saw one Snorlax and 3 Lapras. I have the impression that the gen 2 list is going far better and there are few that I haven't encountered yet (excluding the 3rd evolution of some), but Houndour and Larvitar are unknown to me.

Ivysaur, Charizard, Blastoise, Arbok, Raichu, Sandslash, Nidoking, Clefable, Ninetales, Dugtrio, Persian, Golduck, Primeape, Alakazam, Machamp, Golem, Rapidash, Magneton, Dodrio, Weezing, Jolteon, Flareon, Kabutops, Aerodactyl, Dragonite
Gen2: yet to see Snubull, Mareep and Larvitar

I actually keep a list of Gen 1 mons I have not yet caught in the wild:

Arbok
Sandslash
Clefable
Ninetales
Dugtrio
Primeape
Alakazam
Graveler
Golem
Rapidash
Dodrio
Muk
Electrode
Exeggutor
Weezing
Tangela
Gyarados
Flareon
Dragonite

I've crossed Cloyster and Jolteon off the list in the last few days. I caught all the starter "big boys" (Venusaur, Charizard, Blastoise), plus Charmeleon, during the New Year starter event, and Wigglytuff and Chansey during the Valentine event. I also got Hitmonlee, Machamp, and Aerodactyl during the Valentine event while I was spending hours on end hunting Chansey.

I'm level 36, and have been playing since mid-July. I have all of the above pokemon through either hatching or evolving.

I have seen most of those in the wild. The few gen 1s I haven't seen wild are Persian, Rapidash, Kabutops, Omastar, Machamp.

Gen. I not seen ITW: Charmeleon, Charizard, Raichu, Sandslash, Nidoqueen, Ninetails, Wigglytuff, Dugtrio, Persian, Primeape, Alakazam, Golem, Rapidash, Dodrio, Muk, Electrode, Exeguttor, Vaporeon, Flareon, Omastar. Evolved forms generally seem to be rather rare here, only seen/caught one Jolteon no other Eevee evolution even tho Eevees are common. (Almost Lvl 38, 36,418 mons caught)

I saw a Larvitar as a rare spawn at a Houndour nest a couple weeks back. I imagine he would be a rare spawn at any dark nest if there are any such mons in the game right now with that type.