I have been flying to San Francisco and back since I was a baby in the 60s. I recall my mother having to purchase a last minute fare (perhaps in the early 70s or very late 60s and being staggered that the fare was over $1000 - it was just such a huge amount of money.
In terms of what it was like, I recall well the Pan Am 707s which had to stop at Winnipeg for more fuel westbound but could make it the whole way Eastbound. I recall the open hat racks, which subsequently got filled up by black and white televisions which were for the IFE- barely visible. I recall, in Economy of course, being served smoked salmon, which was a real luxury in those days.
But, I also recall one of my last flights with Pan Am where the food was the worst I've ever experienced on an airline (which IIRC was not too surprising as Pan Am had been going downhill consistently for many years). But the FAs were always really nice.
How does it compare to today? It's almost impossible to say as memories play tricks over such a long period, and points of reference change. I think the seats were more comfortable then in economy, with softer cushions and more space. The FAs were always really friendly whereas, at least on US carriers, they are downright hostile then. But my recollection of the airport experience is not favourable. I remember huge queues to check in at SFO in the old international terminal, perhaps 50 feet deep, with no snake system of queuing. I remember queues for the old, half-baked security, again at SFO,. I remember Customs liked to open every suitcase - this persisted in the USA for years after other countries had abandoned it but I seem to recall Immigration was quite quick. LHR was very different, as you checked in at a bus station in Victoria and got a coach to the airport, which always seemed very civilised.
So it's certainly got massively cheaper. I'm not convinced it's less comfortable, the IFE has improved enormously. The food is probably on a par, the service has deteriorated enormously and the airport experience has improved, apart from US Immigration.