The transistor and the evolution into Jack Kilby's "Monolithic Integrated Circuit" I think was a more meaningful invention than the internal combustion engine.
It's descendants have changed the way we view, communicate, interact and understand the world & universe - not to say the IC engine wasn't a technical achievement in its own right... but as far as progress goes, the IC engine is still used primarily as a means of propulsion for vehicles or as generators.
The Microchip however, has become a vital part of modern life - found everywhere, and its uses still being discovered and designs improved upon.
So my vote is for the Transistor - changing the way we do things since 1947.
🙂