Oh boy. I got into Pokémon when I was 8 and I still love the format. It has a great progression system (at least in my mind) and can be used in easy and super challenging ways, like Nuzlockes. I have way too much nostalgia for the series and I like the music way too much.
My short opinions of the each game:
R/B/Y: Unbalanced, seriously exploitable glitchy games. At least there's no cutscenes.
G/S/C: Terrible level curve, ruins the games.
R/S/E: The first games to really nail the format.
FR/LG: What R/B/Y should've been.
D/P: Great potential but please play on emulator because they're so slow. Play platinum instead and don't bother with the remakes.
HG/SS: Best for a grand Pokémon Game, but still retains some of the bad progression from G/S/C. Still a great game overall
B/W: I have way too much nostalgia for these games but they're some of the best.
B2W2: Less nostalgia but objectively better than even B/W in multiple ways.
XY: Mediocre
OR/AS: Good remake on a great base.
S/M/US/UM: If you like playing Pokemon instead of watching cutscenes, don't play these games. Seriously, don't.
LGPE: Gimmicky games. FR/LG is better unless you really enjoy the Let's Go gimmicks.
SwSh: Mediocre I believe
BDSP: See D/P
PLA: I still need to get around to playing it, gah the backlog is too long
S/V: Actually really great games if you hate how linear other Pokemon games are like I do, and you can look past the performance issues
If you have any questions or comments please reply lol.