>>16592733While the Sinnoh region was good, there was a lot of filler episodes (and I mean a lot). If you want to watch it still, I would just watch the gym battles obviously, the Hunter J episodes, and most importantly, the Ash vs Paul episodes because all builds up to them fighting in the Sinnoh League (which I think was one of the best fights in the entire series).
Or you can just marathon the entire region but its 191 episodes so you have a lot to get through.
