If you are really into this thing:
Assuming you can bring all the present day necessary weapons to the past (nukes, biological weapons, tanks, aircrafts, computers, and other stuffs), you can as well become a god. Obviously you dont confront people at first and you send out biological weapons to the masses. Maybe wait a month, you then disguise yourself as a saint and can "cure" the people with the infected diseases and people will support you. Then you spread more diseases out for many times and each time you spread rumors that this is a sign of bad leadership. You cure the people again and again of different diseases and then claim to be the divine ruler appointed by the god. The people would mostly support you, but eventually the real ruler and his army will hunt you down. You run away and hide while spread more diseases and rumors. Wait like a year (hey you can speed up the time machine eh?) and come back and claim the throne. Drop a nuke in a distance place to stir up superstitions. You should be able to recruit/bribe people easily. You should have an army now and you again spread diseases to the enemy army only, while providing vaccines to your own. Be lenient and allow enemy defections and heal them and you should win and control the people's hearts in no time (speed up the time machine if not fast enough.)
For people who claim that you cant fight against good generals, well, assasinate them first yourself. And to ward off against assasinations, install secret cameras every place in your residence/or have loyal bodyguards. To fight against poison, simply be cautious yourself (you can pretty much avoid poison from ingestion, gas mask at emergency, etc).
Yes, you can change the past and live like a god if you try (for this hypothetical scenario).
But really interesting stuff would occur when you, as presumed godhead, came up against the social expectations on you from your subjects.
Either you fight these, which is akin to turning a supertanker, only worse, since it's an entire society you're up against and the inertia is tremendous. Or you accept the way of least resistance and then it is you who end up behaving as they expect you should. Everyone involved will be changed by the experience of course, but you the modern individual is a gonner, even if you rely on modern technology.
The whole "Go back in time and be recognised as a god due to scientific/technological superiority" is actually the exact same pipe-dream as the 19th c. "Negro-king" fantasy, i.e. find some backward savages and set yourself up as king/god.
And this never happened. The "savages" always turned out to be a damn sight to "modern" and clever to fall for stuff like that. And their technology was usually a damn sight lower than that of the Romans, Greeks etc.
Those historical exceptions there when a westerner WAS recognised as the leader of a native religious movement, considered to be imbued with divine power and all, they either didn't know or didn't quite realise what was going on and kept trying to convert his followers to Christianity. Which was to be expected. In order to be recognised as divine by a society, you have to fulfill their expectations of what that means, not your own.
Someone who was regarded as divine, but didn't know, would seem to have been Captain Cook. If Marshall Sahlins is correct, he paid with his life for not knowing the prescribed annual cycle of comings and goings the godhead he was identified with. Since he didn't keep to the time-table, he was obvioulsy "false", so the Hawaians killed him.
The one who never really got it was the Spanish conquistador Cabeza de Vacca, who in the 1540's escaped slavery in the North American southeast, and became the leader of a religious revival among the natives along the northen shores of the Gulf of Mexico.
He tried to convert his followers to Christianity. They listened politely to this weird man at the centre of their new religion, and then made him heal them all the livealong day. In his account of the experience he specifically mentions how fatiguing his duties as a healer was. He was a very good observer, but as modern anthropologists have concluded, while he was capable of describing his situation, he had no clue as to what kind of situation he was the centre of attention of. (Or possibly he simply couldn't admit any of it to his Christian readership back in Spain. But he does come across as utterly clueless.)
