Excluding ones where he fought with a studio (like Dune or Twin Peaks second season), most of his work is equally "Lynchian" since they are all personal unfiltered films by him.
Inland Empire probably best encapsulates all of his different themes and ideas he goes back to.
Eraserhead is probably his most personal film, and best encapsulates his earlier experimental period.
Mulholland Drive is probably the most polished film of his that combines his early experimental work with his later Blue Velvet/Twin Peaks/etc period. The themes and ideas are presented in a slightly more conventional way while still being mysterious, which makes the film more understandable to someone who is not always a Lynch fan. (For example, Ebert found Lost Highway incomprehensible but loved Mulholland Drive.)
But ultimately yes, I would say if one film had to be picked, Inland Empire best encapsulates all of his previous styles and themes