Not only was Ash dense but the show was a rollercoaster in terms of quality(at least to me). Here's a breakdown of the series so you'd understand it a bit better.
Season 1: Indigo League/Kanto Region + Movie 1. Its intro is what I have in previous Visitor Message and its about the Kanto League or what the Red, Blue and Yellow version games cover(FireRed and LeafGreen are remakes of Red and Blue). Gary is the Anime version of Blue or Red's Rival(whom Ash portrays). Relatively short for a region as its only 80 Episodes(82 if you watched the Japanese Dub. They banned two Episodes for obvious reasons. One was for the use of Guns(where Ash catches 30 Tauros in Safari Zone) and the other because it caused seizures(hence you won't be seeing Porygon any time soon).
Season 2: Orange Islands + Movie 2 <- Movie with Tracy Sketch as opposed to Brock as he left the Anime during this time. Very short season as its only 36 Episodes but the English Dub makes an obvious attempt to show that Misty has feelings for Ash(or is at least extremely protective of him).
Seasons 3-5: Johto League/Johto Region + Movies 3 - 5 <- #3 is pretty good with Entei and Unown. Johto Region itself is much longer compared to Kanto because there's just so many more new Pokemon that they added. Combined the three seasons add up to 157 Episodes and cover what the Gold, Silver and Crystal games do(HeartGold/SoulSilver are their remakes). Johto is considered to be Generation 2 in terms of the games. You'll definitely have some tearjerker moments near the end of Season 5.
Seasons 6-8: Hoenn League/Hoenn Region + Movies 6 -8 <- Misty is replaced with the Female Protagonist in May(the playable female character in the Generation 3 games of Ruby, Sapphire and Emerald). Max is her younger brother who also joins Ash and Brock but I find him to be a useless fourth wheel. Misty does make a few appearances during the series, notably 2 Episodes involving her Togepi(won't spoil it). 144 Episodes for Seasons 6-8.
Season 9: Battle Frontier + Movie 9. This season promotes Pokemon Emerald and the Battle Frontier therein but ironically the Anime has it take place in Kanto as opposed to Hoenn(probably because FireRed and LeafGreen were released at the time to promote it). Battle Frontier arc starts near the end of Season 8 so you kind of know what's going on at that point. Season 9 is 47 Episodes long and is considered to be one of the best seasons since the Battle Frontier's difficulty is said to rival that of Elite 4 members. Personal favorite among many Pokemon fans is Anabel(whom forms a crush on Ash but his dense personality doesn't detect it).
Seasons 10-13: Sinnoh League/Sinnoh Region + Movies 10-13. May leaves the show and is replaced by Dawn or the Female Protagonist for the Sinnoh Region. Sinnoh encompasses the Generation 4 Diamond, Pearl and Platinum Games and is considered to be one of the best series in the Anime to date. Sinnoh Region is 189 Episodes long so its a long one too. You might also notice some Johto promotion within the series and that is because HeartGold/SoulSilver was released during that time along with the games female protagonist in Lyra.
Seasons 14-16: Unova League/Unova Region + Movies 14-16. Not only does Dawn leave the show but so does Brock and both are replaced by Iris(a wild and carefree girl who is a Gym Leader in the Black/White games(White version you face her. Black version has you face Drayden instead) and is the Champion in Black2/White2) and Cilan(Gym Leader of the Striaton Gym in Black/White games. You face him if you pick Oshawott as your starter). Cilan doesn't join the group until Ash defeats the Striaton Gym, much in the manner Brock didn't join the group until Ash defeats him in Episode 5 of the Indigo League. As you may have guessed, this is Generation 5 of the Games/Anime and I find that the games are way, way better than the Anime itself(a shame really). In a way the writers do a real hard reset and try to recapture the magic of the Indigo League but to many fans, they fail horribly and its just a complete and utter mess. I give Black&White or Unova the Black Sheep title but that may be ending after Sun&Moon's time ends. Its still worth watching, just be prepared for Iris to rub you the wrong way after awhile and to not get the development or respect she deserves. Unova is only 142 Episodes long but the final 20 or so Episodes are purely filler that set-up the next region.
Seasons 17-19: Kalos League/Kalos Region + Movies 17-19. Generation 6 or Pokemon X and Pokemon Y is upon you and honestly, the Anime does a better job than the games. That is how much I love this region as Iris and Cilan are replaced by Serena and Clemont respectively. Clemont's younger sister in Bonnie also joins the crew and unlike Max during Hoenn is certainly no useless 4th wheel. In fact, you might come to like Bonnie considerably. A subplot of Kalos is the fact that Serena met Ash when they were very young back in Kanto and when she sees him on TV, she opts to start her Pokemon journey just to meet him. She kind of flails in the wind for awhile with no goal to speak of but it doesn't stop her heart from trying to pursue the dense Ash. The end of the series caused a literal Earthquake in the shipping fandom because well... eh I won't spoil it lol. You might guess what happens just by me mentioning it. Kalos is 140 Episodes long and is so worth the watch. The series has a bit of Hoenn promotion as OmegaRuby/AlphaSapphire or Generation 3 remakes were released during this period.
Sesaons 20,21/ongoing. Alola League/Alola Region + Movie 20-21. The movies are centered in an Alternate Universe so if you were hoping for the Alolan cast, sadly there won't be one. This is Generation 7 and encompasses Pokemon Sun and Pokemon Moon(along with Ultra Sun and Ultra Moon). I'll withhold my opinion on this series but just say I found it to be disappointing. Currently airing so easy to view. Serena and crew from Kalos are replaced by Lillie, Kiawe, Lana, Mallow and Sophacles(5 companions!).
