The Frontier saga isn't too bad, though it's short, you'll be seeing a lot of battles since there are seven Frontier Brains. I remember liking the Ash vs. Nolan battle a lot. There is also a Pokemon Ranger episode with Deoxys as
>>19529938 mentioned so that's pretty neat.
The DP saga is pretty good I hear, especially the Sinnoh League at the end, and even the Grand Festival is great to watch. Ash is the most competent in this saga, fully evolving a good amount of his Sinnoh Pokemon, while using and developing decent battle strategies. It's also the last saga with Brock in, so enjoy him while you can.
Brace yourself for the BW saga though, it's... not that great. It's mediocre at best. Ash keeps his starters unevolved unlike in Sinnoh, and then inexplicably brings back Charizard for no reason towards the later half. Iris is a bit annoying and Cilan's no Brock. Ash's main "rival" Trip is boring. I will admit though I did kinda like how they introduced a bunch of minor characters as other "rivals", though they also unfortunately fall flat except Bianca...
But by far the WORST culprit for "rivals" in the BW series is a little fuck named Cameron. His very existence is what makes me hate the entire BW series. I'll say it now: he is perhaps the worst character I have ever seen conceived for this series. The rundown is basically, he shows up to give Marlon an animated appearance since he challenges him and wins. Cameron's a complete rookie however and gets on by in the Unova League with his bullshit Riolu who then evolves into Lucario. He should not have made it that far at all, he basically defeats Ash and Ash went from being in the top 4 from the Sinnoh League to the top 8 in the Unova League. Cameron then goes on to lose to someone else. He didn't even deserve to make it that far. He doesn't deserve all the cool Pokemon he has. He doesn't deserve to be written as a character.
tl;dr: BF saga's not bad, DP saga's great, BW saga's mediocre because FUCK CAMERON.
