Well, thanks everyone for the comments (even the haters).
Indeed, I never looked into consoles and I doubt I'll do so in the near future.
I would like to reply to few of the questions/comments that were posted, just to "close" this discussion:
a) A good gaming PC is much more expensive than a console.
Not really true: this PC is $488 ($588 if you also need a Windows license):
http://www.tomshardware.com/reviews/build-budget-gaming-pc,4021.html
and plays well at 1080p.
I happen to have bought an R9 270X recently for my 5-years old PC and it works quite well. I can pretty much max out anything @ 720p.
And, by the way, my <$200 270X probably has more "kick" than the GPU in either the PS4 or the X1.
b) You cannot play some very old PC games on modern PCs. True. It is usually an OS issue. I leave it there to avoid another long flamed discussion
c) Can't play Commodore 64 games on a PC. Aside from the fact that you can (at least most of them), via emulator, a more appropriate comparison would have been playing VIC20 games on Commodor64 and Commodore128, all of which was possible.
In any case, my "shock" came from two consecutive consoles of the same "brand" in a time where, you must admit, "innovation" is quite different than the massive leaps that took place 25+ years ago.
d) Consoles have always been that way. True, but there also used to be a whole lot of different platforms (meaning, more competition) and, again, 20 years ago the improvements year-over-year were not comparable with what we have today.
e) I remind that my main gripes were not with the backward compatibility of the games, but with the fact that the SAME
online game (e.g.: Minecraft) does not allow shared games on the two platforms.
f) You cannot play modern PC games on old PC hardware because PC games improve constantly and adapt to the power of the hardware available.
Yes, this probably means that I won't be able to play 2018 games at high settings on my current PC, but if lower settings means something comparable to what I get today, it should still be quite awesome.
g) Last but not least: it is true that much of the lack of compatibility boils down to the use of different architecture (powerPC vs x86): still, this was, obviously, a fundamental decision by MS and Sony when the development of X1 and PS4 was started. Meaning, if they really wanted to, they could have chosen differently.
And again, I totally understand and respect this decision. It just surprises me that so many people choose to follow it: that's all.