The marble question is good. For most purposes I'd say the bimetallic strip (one connected to an actuator at least) is more intelligent than a marble. Studying dynamics of internal properties of the termostat is more fruitful than of the marble that is easy to describe as an unchanging object.

Taken to the logical conclusion, we are all just rolling downwards to a minimum energy state just like the marble.

I don't think intelligence is an intrinsic, let alone binary, property of an object or a system.