From the best to worst:
Gen 17 > Gen 11 > Gen 9 > Gen 7 > Gen 5 > Gen 12 > Gen 8 > Gen 2 > Gen 14 > Gen 4 > Gen 10 > Gen 13 > Gen 6 > Gen 1 > Gen 15 > Gen 3 > Gen 16

Gen 17 is clearly the best because GF finally fixed many broken Ultra modes (like Burthaut, Ticpole, Amonboeba and Tofuru ones), in special Rarecreep Ultra mode that made it Ghost/Pasta type with God Guard ability, and Hitsuda signature move Eletric chair that would Insta KO any Pokémon except these in the White color group instantly.

In addition, Gen 17 brought back the Sex Amie that wasn't seen since Gen 11 (because GF tried to return to the roots a appeal to younger audience again instead of the furry comunnity and +18 public in general, since that the games only sold around 70.000 at the time), this they added compatibility with the Flesh Materialization Device #6 (FMD#6) developed by Microsoft which is pretty great, now it sells around 95.000 copies, a extremely high number that was not seen in many years.

Furthermore, Gen 16 was counting already with 2.400 Pokemon, GF finally disposed of some Pokemon like the Usby, Sandalom, Blowbob and Nike (literally the Nike logo, they were needing money at the time). Now in Gen 17 we have just 1.700, a big change, but for better. I think that my brain stopped counting after the 1.400 ones in Gen 10 anyways.
They also removed the Plastic type, Hair type, Space type, Shit type. They bringed back the Hentai type from Gen 11, though.


Now, going to the point: Which Gen is your fave and why?