Ignorance is a bliss :p (No...I actually want to shoot myself in the mouth and flush the remains of my body down the toilet :( )
Better shut up on things I don't know and talk about what I do know (and know very well): the origins in the new movie line.
Yes it's the Allspark, and no, it's not the Allspark.
Allspark gave life to the first Primes. They be the ancestors of all Cybertronians. We all know the story of the Fallen and his Prime brothers and the Matrix of Leadership. So those Primes died, Fallen allegedly slaughtered every descendant of the Primes on Cybertron save for one orphan who was hidden away. That orphan be named Optimus.
And I have been unable to find out from the stories how did Sentinel Prime survived that holocaust. It wasn't told (as far as I see it's obviously a logical hole; they changed writers between ROTF and DOTM and somehow the new guys must have forgotten partly what was told before, or deliberately chose to ignore it). Anyway Sentinel found the hidden Optimus and brought him up, together with Megatron. They two be his equally best students and faithful followers. Sentinel managed to capture a sun and secure its orbit around Cybertron, thereby powering Allspark for generation of energon to feed the starving planet. This has secured Sentinel's place as sole leader of the Cybertronians, who then were divided only by tribes and no political allegiances. Cybertron's entered into an era know as The Golden Age.
Another obvious logical defect here is that no one knows where the Fallen was and what he's doing during this Cybertronian Gold Age under leadership of Sentinel. It was revealed that he was in captivity in another world, which doesn't make any sense seeing he's just carried out a massacre before everything ever started and with only two Primes survived (one of which obviously a hatchling back then), no one would ever have the power to defeat him and put him into captivity anyway.
The Golden Age ended when Sentinel decided it's time to retire. He chose Optimus to be the new leader as he believed they share the same blood lineage (believed Optimus to be born a Prime). Optimus rejected this unearned power whereas Megatron, overheard their conversation, got jealous and thought Optimus's refusal was a sign of his weakness and ineptitude. Sentinel retired splitting power equally between his two students, with Optimus in charge of science and history, and Megatron in charge of the defence force (how on earth is that ever considered equal I'll never understand).
Naturally Megatron took full advantage of his power, gradually turned the entire defence force into his own army. Meanwhile Optimus was too preoccupied with his scientific research and archaeological excavate (and too trustful in Megatron) to pay attention to the silent change in his power. Optimus's excavate achieved breakthrough when he reached the geological layer of the Prime's era, and uncovered an intact plate with a Decepticon badge on it. Megatron took possession of the plate, later found out it was a gateway of communication between him and the Fallen. The Fallen thereby took command of Megatron, promising him of unprecedented power should he succeed in erasing out Optimus and his followers and the human race on earth. At the same time, Optimus has came to the conclusion based on his archaeological evidence that he was indeed a descendant of the Primes.
Sentinel during this time, as Optimus wishfully believed, was enjoying his retirement, away from all Megatron's scheme, whereas in fact he had secretly formed alliance with Megatron, deeming Optimus unfit to lead, all of which lead to his later act of betrayal on Prime.
The First Gunshot at Lexington for the Great Cybertronian War officially took place when Megatron ordered Prowl and Bumblebee to arrest Optimus and his fellow bots of science on charge of treason because Optimus "broke into" his quarters to check out the plate while he was away on an invasion battle. Starscream set ambush on the autobots en route but was defeated by Optimus, who lead his crew (together with Prowl and Bumblebee) to successfully break the siege and got away. It was from there that Optimus openly announced himself as Optimus Prime and officially assumed leadership of the autobots as he deemed himself "earned" the power.
The rest of the story, we all pretty much know (unless you haven't watched any of the 3 movies). The Allspark in essence served no more than an excuse/mean of war as it represented power and control over the people. But in the very beginning, the origin of the war was more like a "sibling contest" between Optimus and Megatron, evolving finally into a war under Megatron's jealousy of Prime and ever growing thirst of power.
Yes it's lengthy...I trust I haven't missed any logically material details.
Movie origin was IMO one of the best TF stories ever written, regardless of its logical flaws, as it explores a deeper and more conflicting humanity running inside the main TF characters, making them more real and closer to feelings. Classic G1 is appealing as well but way too naive in story (after all I started watching them when I'm already in my late 20s).
And my comparison is drawn on my own TF knowledge library that consists of three new movies (together with their complete prequels and sequels and everything else related), the first five Madman G1 episodes, the 1986 movie, random bits and pieces of IDW's new publications and zero anything else.