I would say Jimmy Stewart. His career spanned several decades. He was an Academy award winner. He was in great films encompassing a number of genres: Westerns, sentimental Capra films, Hitchcock/Suspense films, Crime/Courtroom thrillers, Biographies, comedies, etc.
I know it doesn't make him a great entertainer but he was a good man. He was married to the same woman for decades until she died. He volunteered for the military prior to WWII, entering as a private. He flew bombing missions over Nazi-occupied Europe. He was awarded the Distinguished Flying Cross and the Croix De Guerre. By the end of the war he was a Colonel. He stayed in the Air Force reserves until 1968, reaching the rank of Brigadier General.
Unfortunately, Hollywood doesn't have actors like Jimmy Stewart these days.
"Be of good comfort, Master Ridley, and play the man! We shall this day light such a candle, by God's grace, in England, as I trust shall never be put out."
--Hugh Latimer, October 16, 1555