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Johto is nostalgia bait. You get 2 mid tier regions in one package. For being the first two they aren't bad, but by far aren't the best. Gen 3 easily beats Gen 2 by the selection of pokemon, region, and story. I wouldn't even said Gen 2 really had a story. Gen 4 is around the same level as Gen 2. I think the region bumps it up a few points. Gen 5 blows everything I've mentioned out of the water, both BW and B2W2 are phenomenal games in terms of story, region and gameplay. Gen 6 and onward can be debated, I personally would rank gen 6 higher because that's when I started playing pokemon games. Gen 7's island theming is way more creative than Kanto DLC. Gen 8 and 9 are up for debate. I enjoyed them, but they are objectively pretty bad games.
So I feel like Gen 2 would rank around 6 or 7th place on a ranking. Weak pokedex, weak region and weak gameplay wise. Most people are biased towards it for nostalgia.