Remembering Sir Patrick Stewart, Captain Picard and Professor X

Sir Patrick Stewart, the actor known as Captain Picard in Star Trek and Professor X in X-Men, has died aged 86.
His family said he died in the loving care of his wife Sunny following a brief and poignant journey with Alzheimer's disease and Lewy body dementia.
So what made his work, from Shakespearean stage dramas to Hollywood, span so many generations?