I'm never at a loss for entertainment on a flight these days thanks to an iPad. I can read, write, or a thousand other things to whittle away the hours. I was a bit surprised to learn (but shouldn't have been, really) that much of the food service at for example Pan Am was in and of itself a sort of entertainment. Especially in first class. Tourist class being a much smaller affair, and I suppose had less of an entertainment value as a result. Aside from which offerings of magazines was really one of the few things that could be called entertainment. Well, aside from a book or a view out the window as dixi88 mentioned.
I've tried to find travelogues that describe the longer transatlantic/transpacific flights to get more of a sense of what a trip was like. But no luck so far. Or rather, not in-depth enough to sate my curiosity.