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3 > 7 > 5 > 4 > 2 > 6 > 1 > infinite powergap > 8 > 9 > whatever garbage they're pumping out these days
3 hit the sweet spot between too much bloat and simplicity. They're perfect. There's a reason they're still the most consistently played of the series to this day.
7 trumps 5 for the technical capabilities i.e. widespread connectivity e.g. of trading, battling, number of gimmicks, number of mons, things to do for meta gaming, in-game, shiny hunting etc it was the peak of that stuff, but 5 are better games for a single playthrough/story.
7 was the finale of the series.