Nothing compares to the first season of Pokemon. Seriously.
It had a heart back then. It wasn't ever repetitive or obvious.
Ash was just a starting pokemon trainer, and that was the time where he learned about Pokemon, and so did we, cuz back then, most of us were all 5, 6, 7, or 8 year olds!
So we can all relate to how Ash was in his very first adventure, unlike now: We've learned and grew up...but Ash hasn't really changed. He's still opening up his pokedex to pokemon he's already seen, or acting all surprised when Team Rocket takes off their obvious disguise.
Back to what I said before, there was a HEART. The animation now seems blocky and bland. As if they were all painted on Adobe Photoshop. But the old animation style...I dunno, it makes the characters just seem more real, life like.
Just my 2 cents. Nothing can, will, or is able to compare to the Indigo Saga.