I’m not sure I do have an opinion on that. Like, obviously they’ve been improving over the course of the franchise’s lifetime, but just as obviously I’ll be lynched if I say that I and II were clearly the worst. Also they’re not uniformly better and worse at everything they do. Like, V in my opinion has the best story, but I was never wild about its Pokémon designs, IV made some really important changes to the game mechanics but does some kinda screwy things with the world-building, and III was basically decent all around but nothing really sticks out about it for me other than its unique musical style. It’s sort of difficult to say “right, this one was overall the best,” because how on earth do you compare things like that? VI was just pretty solid all around, I suppose, and I liked aspects of its general design philosophy, which makes me optimistic for when I check out VII.