Definitely agree with a lot of the reasons stated above.
For me, I remembered the original film from my childhood, but seeing it as an adult, I fell in love with it all over again for its characters and for the heart-wrenching story.
I’m currently making my way through the rest of the series. As of this post I have made it to the fifth film. The original is still my favourite, but I still love the characters and I wanted to see what further adventures Littlefoot and his friends would get themselves into. My favourite sequel so far is “Journey Through the Mists”.