The ending implies a horrifying cruelty to me...

I've read the threads saying:
a) It's a dream of what WOULD have been had he chosen different
b) It's a fantasy, get over it
c) It is a glimpse, of something he missed out on, but is still not too late to grasp (of course starting from scratch and 13 years older)

And so and so...

But all of them pretty much ignore several crucial facts:
a) If it's indeed a supernatural glimpse, it's the cruelest one I can imagine. For it's clear he CANNOT have that life nor loved ones any way you slice it because:
- Such life is attained after +-13 years of living it. Do the math, he'll be 50 by the times he gets there, let's see how much energy/love is left in there.
- As stated elsewhere, the kids won't be the ones he met. Who knows how his new ones will turn out (he could end up with a Down, a school shooter, you name it) or that he or her can have any (or want, what if she doesn't want any?) to begin with.
- As others have stated, they are one bad day away from being ruined. Let's see how good that life seems then...
- Wanna bet Kate is still available (boyfriend, divorced, kids, etc), interested, desirable (what if she got AIDS?), still a good person (career climbing can turn Mother Teresa into a class A @$$hole), you name it?

See where I am going?

If he dreamed the whole thing, perfect. Go get yourself a wife, maybe even Kate if you're really lucky. But don't throw your career away!!!!! Unless you wanna bet your new life on Kate really having an uncle Ed. And especially be prepared for some mayor disappointments when your new life doesn't measure up to the dreamed one...

If he did not dream it, then it's even worse. Why give anybody a sample of something they can NEVER attain? That was considered torture in ancient times (tantalizing), similar to taking an orphanage/street boy to Red Lobster just long enough for him to smell, touch and even have a small sample, only to send him back to his previous situation and cut him loose, knowing full well he can NEVER either forget/attain it?

So for me, the ending is a cruel joke played on Cage. It doesn't quite sink in only because the movie ends before we see how things went down between him and Kate, thus providing FALSE hope (as in Pandora's box, the hope that remained there was actually false hope, hence why it was there alongside all other evils, for ancient Greeks were pretty aware of the bleakness of their situation, prospects and knew better than rely on the god's flimsy whims)

To provide a better example, anyone familiar with The Punisher comics knows that Frank Castle's worst nightmare is NOT dreaming of his family's death, but to dream a "glimpse" of what his life would be had they not died, just long enough for him to begin to believe it, only to then wake up...