My favorite is DP. I really liked amazing and in-depth villain arc that it provided. Paul, as I mentioned is the best Ash's main rival and his story is simply astonishing in entire animeverse when it comes to rival stories. Ash's team was brilliant, not too OP like in XY and Buizel and Gible didn't evolve which I kinda like that they didn't evolve. Even though I prefer final stages in my playthroughs, it's kinda sweet to see 1 or two non evolved stage by Ash. Dawn's team and development are good. I liked many gym battles, league( which is still the best) and I liked other battles especially Ash vs Paul ones. Ash's and Dawn's rivals were great.
9/10
What I didn't like about DP is: Dawn's Piplup, fillers between: 7th and 8th gym, Brock's lack of development.
Second favorite is XY. I really liked Ash's team and I liked what they did with Greninja. Rivals were a little on side-note but it was fresh that Alain was introduced with different goal in hands than Ash. I liked villain team plan but IMO it's not as good as Team Galactic one. Still this is second best villain story in animeverse. I liked what they did with Serena and gave her some development. Clemont's story is also good especially with Clembot. I like fresh idea of preforming instead of contests but it kinda felt not for my taste. I liked animation and I don't know if they really gave all budget on this but it really felt way different than any Pokemon anime series. Fillers were good and enjoyable since TR has become more competent. Other rivals were kinda meh in comparison.
8.5/10
What I didn't like: Ash not getting Mega Stone, Kalos league could've been better, Sawyer's clingy attitude towards Ash, lack of captures for Serena, preforming could've evolved some Pokemon battles
My third favorite is AG + BF. I really liked Ash's team on here with great group dynamics but they fail to compare when it comes to his XY and DP teams. I liked how he used other Pokemon in BF. I found BF better than AG. Fast paced, more battle oriented and enjoyable filler. Sure, AG did have them too, but some of them were pain to watch. May's team is amazing I'd say even on par with Dawn's. Brock has some development there unlike in DP. I found Max better than Bonnie anyway. Hoenn League is second best and BF Frontier challenge are one of the best challenges Ash has even had. May's rivals were good, maybe on par with Dawn's.Honestly, if Team Aqua and Team Magma arc was much much better , AG would've been better than XY,IMO.
7.5/10
What I didn't like: some fillers were bad, Ash's lack of rivals, Ash not using reserves in Hoenn league, Villain team arc(Team Aqua/Team Magma) is really bad, the worst one so far.
My 4th favorite is BW + DI. I know this is really unpopular opinion when it comes around, but I can't help but to like it. I really liked how many Pokemon Ash captured but that pays the price sadly since writers could've easily made it work. I really liked Iris and Cilan as companions. I found Iris better than Misty,Bonnie, Clemont ,Mallow, Sophocles,Max and Brock(DP) when it comes in character development. Her attitude is kinda annoying together with the voice. Cilan is very likable, I don't know why his "It's tasting time" is worse than Clemont's "Clemontic Gear On", both are bad but have some charms in it.I really like tournaments in it. Rivals are good/ok since I like angry rivals more than calm ones. I liked Team Plasma and how TR got actually antagonistic in this series.Fillers were also kinda enjoyable except DI fillers.
6.5/10
What I didn't like: Iris being annoying, Ash's reset, lack of "evolving time", Unova league could've been better, DI could've had one tournament where Ash wins
Since we have OS, I am gonna split it into Red and Blue with OI and Gold and Silver since it's kinda unfair to compare 300 episodes with 200 and especially 140 ones...also, I would like to split OS into Japanese and English Dub since there's a difference in my liking.
My fifth favorite is R/B + OI ( English). I really liked comedy in here where Ash roasts everyone. This is the only time Pokemon was more sitcom-y and actually funny to me: non Japanese cultured guy.Part from that I liked how kinda serious TR was in here and it had some TR development. I liked Tracey aswell. Gary is IMO fourth in rank Ash's rival: first being Paul, second Alain, third Gladion and Gary comes in 4th. I liked how many Pokemon Ash caught and I liked Charizard's development.It was short and fillers were amazing.
6/10.
But here's what I didn't like which would justify the rating: Ash releasing everyone and not reuniting with them, Ash catching 30 Tauros, lack of battles and battles were really bad, Kanto league is the worst. Ash at most time had only 5 Pokemon in hand.. which made lack of development for Tauros, Muk or Kingler(Krabby).
Now I am getting in territory where remaining series are not my favorite but they go from ok, mediocre.and bad
Ok one is SM. What I liked about SM: Character development for Lillie,Lana and Kiawe, I really liked Kiawe's Charizard,Marowak and Turtonator, I liked some of Alola league's battles making SM series enjoyable only in the end but that's not enough to make my favorite. Ash vs Kukui is third best battle, first two being Ash vs Paul SL and Ash vs Alain KL. I liked Ash's Alolan team but I don't find them better than XY and DP teams. I like how competent TR was in here. I liked little sub plots that were going on ( Lusamine, Necrozma and Dia) but they lack to be better than BW's plots. If Necrozma's plot was better then it'd be better than BW's TR and TP plot.
5.5/10
What I didn't like: Oh boy, I didn't like first and foremost; lack of battles, they were mostly one shotters by Z move, that's why I enjoyed SM a lot more near the end where it's too late, I didn't like really bad slapstick comedy in making "funny faces", those faces are way different than PM faces if anyone seen those: PM faces were normal anime ones that occur in all anime series with little more detail added to it, still they're kinda passable or meh, but SM faces are what I, and probably others calling them: JoJo faces. Where they change the art-style of characters to be JoJo like. In PM they don't change the art-style to JoJo when changing the faces which is a plus. I am not hating on JoJo or anything but that's cringe-y( putting different art-style to add comedy effect). If SM's faces were like new PM faces( BTW, PM is my shortcut for new anime: Pocket Monsters), it'd be fine, still criticized-prone but not as cringe-y as JoJo faces. I disliked Mallow and Sophocles development they felt like supporting characters. I dislike that they made Lycanroc and Rowlet kinda overrated and I disliked that they didn't make Gen 8 Pokemon and gimmick in SM. Maybe Kukui to Dynamax a Pokemon.Alola league could've been much better,though. Many fillers were bad only a few ones were good.
Mediocre one is G/S(English). Comedy was still there which was good, Misty's development rocketed but Brock's kinda fell down a bit. Ash's team was really bad since almost no Pokemon evolved during Johto except Bayleef. Fillers are really atrocious. It lacked rivals, villain arc( TR fell down in Johto). Johto league and comedy were the only good thing about Johto arcs.
5/10
And finally bad ones are OS( Japanese). Reason why I found these bad is because: comedy that existed in OS ( while it faded in AG in both versions) were made for Japanese people which I of course, would find it weird. 4kids made it more for us to understand and made punchlines really stick. If we remove comedy from Red and Blue + OI (English), then that series would be as bad as Japanese OS is. Comedy really saved first series(English), IMO.
4/10
EDIT: Updated scores
DP: 9.5/10
XY: 9.3/10
AG:8/10
Kanto and OI:7/10
BW: 6.5/10
SM 6.3/10
Johto:6/10