i still like crystal and HG/SS the most casually. emerald and platinum are right behind that. though i still enjoy gen 1 a lot because i know more about the games than 99.999% of people do.
I am surprised that you guys don't consider the newer generations. For me at least Omega Ruby is my favorite, it used to be Sapphire but yeah. After all I prefer the new things like physical/special attacks and the choice of pokemon you have.
Definitely Pokemon Puzzle League. Pokemon Snap was also great. From the handheld-editions I find it difficult to favor specific ones. Probably Crystal? I really like the new combatsystem from Gen 4+5 but in terms of the amount of Pokemon it starts to become too much (and I despise the mega-evolution concept) and Crystal was superb with that multiregion-approach. That being said, I never got to play the remakes of the 2nd Gen so I might like those even more. The more defensive metagame in the first 3 gens also appears more attractive to me when looking at competitive.
White 2 and HeartGold ~ I prefer HG/SS rather G/S/C because there is a better version of BGM of Route 201 than in D/P/Pt xD Also the GB player in HG/SS is quite good as it contains some 8-bit BGM even if it didn't appear in gen-2 games. I personally do not like OR/AS :/
Pokémon Emerald. It was the first one I played and still go back to playing it. Gen 3 overall is my favorite, really. I still have the green cartridge (though no gameboy to play it on).
Pokemon Diamond and Pearl. Probably because that was my first. The funny thing is that I didn't even realize that there were games and I thought that it was just a TV show and when I saw Diamond on the store shelf for the first time I thought to myself, "Wait, they made Pokémon into a game?! I need it!!!" Replayed it last year and it brought back a lot of old memories.
Heart Gold and Soul Silver are probably the best. I cannot recall a game with two regions. Platinum and Diamond hold a special place in my heart too though.
I only played pokémon black and white and a little bit of pokémon go
I don't really have an opinion on pokémon related subjects anymore but if I had to choose it would be the black and white series
I'd say Emerald, so I thoroughly enjoyed ORAS, but gen 5 holds my favorite poke, so I'm pretty torn. S/M; US/UM are fun, but not as much as ORAS, imo.
Aaaaaa, but Sinnoh!
Dammit, I like all of them.
Emerald was my favorite for sure, I'll never forget climbing that tower for Rayquaza in some random restaurant when I was like 6. I think I spent the most time in Diamond though