Maybe because it's so relatable..
We all lost someone/something in our lifes,and return after many years to see it. And you can only feel is pure happiness.
Even though this scene is sad,but when Alan yell 'mom-dad Im here' and running on streets you just can't feel bad..
Because it's so full of life. Alan is 35 years old in the body of 10 yo. He firstly don't realizes this,but soonly he does. His extremely tough life in jungle teaches him valuable life lessions.
Jumanji has to be one of my favorite movies ever. Its certainly my favorite movie growinth up.