Some might give more weight to the telegraph, the camera and small electric motors.

The telegraph is significant because it is the beginning of real-time electronic communications.  Since electricity moves at the speed of light for all intents and purposes the telegraph was instantaneous.  The lack of prompt communications can be disastrous.  One need only note that the Battle of New Orleans fought at the end of the War of 1812 was really fought two weeks after the peace treaty ending the conflict had been signed in Europe.  that battle which would guarantee that Andrew Jackson would be called for the rest of his life "the Old Hero," cost the British 2600 men.  They were lost for nothing.

Convert the electronic signal of the telegraph to a sound signal and you have the telephone.  Make sound signal wireless and you have radio.  Why not ad a visual signal to the sound signal?  Now you have television.  It is but a short jump to the internet and WiFi.

The camera changed art forever.  Modern photography dates from the 1820's.  No longer was realism "capturing things the way they are," dependent upon painting or the process of sculpture.  The camera captures the present.  The camera led to the wide variety of modern art.  Light, color, shapes, materials, and ideas themselves became the subject of pictorial art.  Monet, Picasso, Pollock and countless others were free to paint whatever they wished.  Photography would present to the world as it was.

The third invention for our consideration is the advent of small electric motors.  Small electric motors are all around us.  Many are so cheap as to be disposable as in the case of our electronic toothbrushes and vibrating razors.

Consider that in the early 20th century you had to crank a car's engine in order to start it.  Not all women possessed the necessary strength and what gentleman would allow a woman to crank the auto when doing it incorrectly would make the crank snap back resulting in a broken wrist or a broken arm?  Enter the small electric motor, in this case, the electric starter.  Women no longer needed men to drive them places.  The electric starter liberated half of the population.

The started changed fashion as well.  Who could drive an auto in the full skirts that propriety required.  Fashions had to change even perhaps resulting in women wearing slacks!

There are many other candidates for greatest inventions:  Modern drugs, the automobile itself, the airplane, and the integrated electronic circuit spring quickly to mind.  The real goal I think is to look with fresh eyes at the technological world around us, even the uncommon history of common things.  Sliced bread dates from 1931.  The ball point pen appeared in 1935.  Technology is what people do.