For me, it's all about the village scene where Indy translates the story of the missing stone.
Despite the broad attempts to inject comedy, there's a certain weight to Ford's performance in TOD. I also like the reluctant hero aspect of it, and the fact that it's filled with iconic Indy moments (ie. rope bridge; the mine cart slowing revealing Indy to the Thuggee guard; etc.)
It was a bold move to follow Raiders with such a dramatic departure. Not everything works or holds up 20 years later, but it's definitely a worthy entry.