When I was younger, I followed Pokémon almost religiously. The first season especially had some good moments. "Bye Bye Butterfree" comes up in my mind as the most poignant episode I've ever watched from back then - it even had me in tears!
More recently, about four years ago, it was actually Keroro Gunsou (what is now known as Sgt. Frog) that got me back into watching anime actively to the point of going out of my way in order to look up subbed anime. It was hilarious for me to watch back then.