IMHO I think that your view regarding that "people should take care of their parents when at all possible and that is should be as basic an obligation as caring for their children" is somewhat idealist.
I had no issues with looking after my grandmother as she took great care of me and whilst I would likely do the same for my MIL, would very likely NOT do the same for my mother. Family history (and the fact that I had to live with my grandmother rather than mother from my teens for my own wellbeing) has meant that too much "history" precludes such an option in that case It seems harsh but for my own well being and sanity I couldn't do it, even though I'm now on quite good terms with my mother. Sorry, I digress...
My point is, every situation is different and only those directly impacted can really ascertain whether providing such care/moving in is an option for them and so many variables come into play.
I do think, however, it's perfectly valid for you to share your views with your friend regarding what you would do/suggest (especially if you're so close and he is asking you for opinions). But, as a true friend you should support him 110% whatever decision he decides to make. Life's not straightforward with clear rules that kids should take care of their parents in their old age (in an ideal world, that'd be, well, ideal!), but it's not possible for some for so many different reasons, so please don't pressure him.
And another way you could really provide help would be to visit his father yourself, if at all possible. A few of my friends did this with my gran (not often, but sometimes), and honestly, she loved the variety of conversation that provided.