Final Gen 1 (Regional) dex entry
Answers
If also excluding legendaries, my last entry was Aerodactyl (hatched in May 2017) and my second-last was Lapras (caught during an event with SGPokeMap). I also remember Machamp and Seel were among my last few entries.
As for legendaries, I got my first Mewtwo last Friday and have yet to redeem my Mew despite having completed the Special Research.
The Snorlax with Body Slam from research breakthrough last week completed an even more significant achievement: a Gen 1 living wonder dex (excluding regionals and legendaries)!
Excluding regionals: Articuno.
Also excluding legendaries: Muk. For about a year and a half I only saw like 6-8 Grimers and hatched none. When Muk was a raid boss, the system was so buggy and my attacks were so often not registered that I couldn't solo Muk, despite having a team theoretically more than good enough.
Almost one year and a half to hatch my first Snorlax as well, but I caught a wild one months earlier. Just one though!
Evolving a Dragonite was my last entry (excluding regionals and legendary)
Female Snorlax was the last of my full male/female gen1 dex.
I had a female before that, but she arrived before they counted gender in the dex, and so waited a long time until it could be marked in the dex.
For regionals, I am still missing Mr Mime and Tauros
Aerodactyl, Q1 2017. I'm still missing Kangaskhan and I don't know if I want to trade for it - the other 150 I caught myself and I am sure a Gen I legendary will go walkabout in November. I've got a 2/3 chance of it being Kangaskhan (either generally or meandering to the states when Tauros goes global)
I only need mewtwo. Other than Mewtwo I have all of gen 1 including regionals. I play in a fairly robust and adult-driven pokemon go community. Someone is aborad almost all the time. Currently one of our group is in on vacation catching oodles of Mr. Mimes. When she comes back our group will likely all have 'em.
In fact, I'm only missing gen 3 regionals to complete my dex entirely. My dex shows everything I've seen as also being caught.
Chansey, caught wild during the February 2017 Valentine's Day event. The number of hours I spent hunting for Chansey during that event was insane, probably an average of 6 hours per day. I was obsessed, like Captain Ahab hunting Moby Dick, driving all over the metro area cruising mall parking lots and other reported sighting spots. After a while, I was ignoring every other pokemon (Porygons, Wigglytuffs, etc.), to make sure I didn't miss a Chansey. Late on the night of day 5 (1:00am, actually), I had a Chansey shadow appear on the in-game tracker, and when I headed for the pokestop, it turned out to be in the center of an indoor mall, which of course was closed. I spent almost an hour trying to figure out a way to get to it, with no luck. I was livid, and was almost ready to quit the game. The next night (day 6), I finally caught one in a mall parking lot, and another about a minute later in the same lot. The feeling was more of relief than joy, as I knew I could stop the insanity. I still have that first 28% Chansey to this day, despite having transferred many much better ones, and it remains arguably my most memorable catch.
I am still working on my "wild-caught" gen 1 reqional dex. I caught a wild Electrode for the first time last week, leaving only seven gen 1 mons that I have not caught in the wild: Clefable, Primeape, Alakazam, Golem, Gyarados, Flareon, Dragonite. I never used 3rd party trackers.
I've gotten two wild Jolteons, probably a dozen Nidoqueens, and two Charizards.
Before I had a Nidoqueen, I just needed one more Nidoran-F to fully evolve one, and I actually ended up catching a wild Nidoqueen first.
Catching my first wild Charizard was sort of a mini version of the Chansey quest described above. During the New Year's 2017 starter event, I caught multiple wild Venusaurs and Blastoises, but Charizard eluded me until late in the event. I was going out for a couple of hours per night just to try to find a Charizard, and finally got one near the end of the event. It wasn't on the in-game tracker; I stopped to catch something else, and the Charizard just appeared.
The other Charizard was on my way home from a Mewtwo raid (the only time out of six that I failed to catch the Mewtwo). It was this past Spring during the Kanto event, and a low-CP wild Charizard appeared. It was a double candy event, and I pinapped it for 40 Charmander candies, which are hard to come by in my water-ice biome.
Most people who travel are probably more likely to visit somewhere in Europe over Australia. This not only means more people can catch Mr. Mime themselves, but now that trading is available they're a somewhat readily available regional as long as you know somebody. I personally caught mine during a week in Amsterdam last fall.