3>4>2=1>5
>>7>
>>6>>
>>83 has the best version of Kanto (FR/LG), runs the smoothest at the highest frame rate, and is not absurdly broken. Introduction of double battles the best gimmick in the franchise. And the Colosseum games with all double battles show a great way to design a good hard mode in future games.
4 started the slower frame rate, has severely glitchy screen transitions, and Diamond and Pearl are atrociously slow games. But the Pokémon designs are solid, HG/SS are solid games, Platinum is a good experience, and the physical/special split makes a lot of Pokémon more viable. Overall, very positive despite the bad start.
2 is very similar to 1, acting as a fix to the glaring issues. But the game suffers too much from sequel-syndrome, and is not as fun to play casually.
5 I can respect for avoiding Gen-1 pandering and making you use all new Pokémon for the first games, and doing a real sequel instead of a 3rd version. The art style just started failing, the shading and scaling was screwed up, and the games will chug at points.
I haven’t played PLA yet. Maybe that will improve my views on 8. But the base game was more expensive for less content than 7, has the audacity to charge for online play (which 7 didn’t do), and it killed itself before a 3rd version or sequel, which I want because the wasted good characters (Ball Guy, Marnie, Sonya) on such horrible writing. At least 6 wasn’t wasted potential.