>>53045408There isn't one.
Gen 1 is a great and cohesive experience but it's a buggy and unbalanced mess.
Gen 2 refines the system completely fails the region it's debuting for the false promise of a second region that is only a shadow of its former self and wrecks the level curve - plus its new mons are consistently hidden away instead of showcased.
Gen 3 introduced a bunch of cool new features but literally has too much water and doesn't even let the rival challenge the player while the remakes are full of artificial restrictions.
Gen 4 finally gets the balance about right with the physical/special split but has a terrible engine that is too slow in both its new games and the remake.
Gen 5 has an incredible story in both paired versions but its mons are 50% lazy recycles of Kantomons and it's honestly really ugly.
Gen 6 took some bold steps forward graphically, attempted another rebalance and really tries to create a child's adventure but is filled with empty promises of a second paired version that never comes and the postgame content is gutted, plus spends too much time pandering to genwunners. Its remakes are a step down from the Gen IV ones, refusing to use the third version's improvements.
Gen 7 shakes up the formula in a lot of bold ways but is entirely too easy, filled with cutscenes, and doubles down on the Kanto pandering to an extent gen 6 shied from. Its remakes are atrocious and have no redeeming features.
Gen 8 has a great idea in the Wild Area plus tries to reimagine the League but then it dives straight into Dexit, makes the game even easier than ever, and quintuples the Kanto pandering. The remakes are utterly uninspired and the pseudo-remake has a lot of good ideas but has content that expects you to have played the initial remakes first.
Gen 9 finally goes fully open world... and immediately bungles it by not having a better handle on how players level through playing.
You can't objectively rank them because the pros and the cons are subjective.