It could be that Sam realised that his life in the 70's meant more to him then he realised, real or not, and decided to return to the past. Not because it was any realer, but because he felt more alive there.
That was my take on the final episode too, he no longer cared which was real, except that he preferred 1973. However I was disappointed with the deliberate ambiguity, and I thought it extremely muddled. I videoed this and watched it after the rest of my family did. They were very confused and still aren't sure which was meant to be the reality.
I always saw this along the same lines as Iain Banks
The Bridge, so I always thought that he was in a coma, but the addition of the
Vanilla Sky jump, the M.A.R.S. operation, and the lack of explanation about many other things - Annie's psychiatrist boyfriend from the first episode, the fact that Sam never attempted to speak to ex-girlfriend Mia before jumping off the roof, that he had met himself and his mother but also saw those gravestones - it didn't quite fit. And as jackokent said, his colleagues were very forgiving when he returned, too forgiving for it to have been reality.
Jumping off the roof, would no doubt lead to death rather than another coma, so as Coolhand said, the girl turning off the TV could well be the end of his life.
There is another possibility, that during the coma he went to that plane that exists between the states of life and death, and so he died and went there to stay.
It is all very philosophical, and I was looking for a straight answer with a yes or no. This ending will be long debated I'm sure. It will be like the ending to
The Prisoner. I just hope the ending to
Lost is clearer.
Best line:
Sam: Was she enigmatic?
Ray: No, she was from Barnsley!
As for a sequel, well, very predictable but unlikely to strike gold twice.