Life on Mars has come to a final end, although the plot ended on a rather ambiguous note. Really, what happened is up to the viewer :)

Read on for Justice!

Sam does finally wake up in the the present, with the surgeon noting it was a tumour (in a room labelled Hyde 2612). He operated and Sam wakes up, happy as normal. Later on in a meeting, he cuts himself with what looks like a pen, without even noticing it. He remembers something Nelson (The '73 barman) told him; When you're alive, you can feel it. Not feeling it, Sam concludes that the present lifetime is false, that he really is in 1973 and that the present (or future 2007) life is just in his head. He goes to the roof, and jumps off, returning to the spot and time in 1973 he departed. So it would seem, from the show that the future 2007 lifetime was all in his head, there was no tumour, and he really is in 1973. There are however mutually exclusive ideas that each could support either theory;

He jumps off the building; if he indeed was truly in the present day 2007, this would have killed him. If he was dead, he wouldn't have thought anything, and would have simply died, without returning to 1973. However, if he was indeed in 1973 and the future was in his head, this action would not have killed him and he would return to his current and true life in 1973.

He has knowledge of events, technology and theories pertaining to 2007, such as (in a previous episode), the stinger (spikes on chain to blow car tires), computers, modern (2007) policing practices. Logically, if he truly were in 1973, assuming the world Sam lives in not parallel to our own, he could not possibly know this without having travelled in time.

The stronger side seems to point that Sam is in 1973, although the knowledge of 2007 is puzzling. I guess there really is no true answer. However, there is one third and final theory that supports all the above points, and adds up; Sam really is from 2007 (Satisfying knowledge of modern day), is in a coma (satifying the 1973 situation), but never wakes up (satisfying jumping off the building and not dying). Sam still being in a coma and never waking up but having a brief stay in 2007 could be symbolic of the attempt to remove the tumour failing (jumping off the building).