Actually with movies like 3 idiots, taare zameen par and rang de basanti its quite difficult to pick one....
I would rate them in the following order: 1. Andaz Apna Aona 2.Taare Zaamein Paar 3.3 idiots and 4. Qayamat Se Qayamat Tak
there are a lots and i cant judge one of them but still here is short list: Ghajini Lgaan Sarfrosh andaj apna apna rang de basanti..
all the movie of aamir khan are best but i tell the name of few best movie of aamir khan are: -Dil chahta hai -Taare Zamine par -Ghajini -3 idiots -Rang de basanti -Lagan