I've always been confused by the attention and plaudits received by Halo; it was fun to play and looked pretty good, but, if you'll forgive the tautology, it brought nothing new that hadn't been seen before.
As an aside, if the much-quoted regenerating energy is to be considered new, then I would have to say that expectations of originality have fallen somewhat dramatically over the years. It seems like a forgotten placeholder or an over-simplified game mechanic; not having do anything but stand still to replenish your shield instead of, say, eating grass or finding a power outlet indicates more of a cop-out than a plan.
If the original plans had been followed and Halo had been released for the PC, it is unlikely that it would have risen above the standard fayre on the market (which when finally released for the PC, it didn't). Maybe it is simply that people who had bought an Xbox were desparate for a specific game worth playing on their system to use as a justification as to why they (or more likely, their parents) didn't get an actual game console, but ended up with a re-badged PC.
To take that a step further, it may even be considered as the likely start of rabid fanboism on game forums; the denial of any rationality outside of a chosen brand - be it Halo, Sony or any other irrelevant name or symbol. I, for one, could never forgive any company for being the cause of that.