It seems that the only reason Voldemort needed to kill Harry Potter was the prophecy. Harry himself didn't possess any special powers and was only spared from death thanks to the sacrifice of his mother.
So what would've happened if Voldemort had simply ignored it? Would he have won the Wizarding War once and for all?
That is, free will vs determinism all over again. JKR's stance is pretty clear on it:
" Destiny is a name often given in retrospect to choices that had dramatic consequences."
And again from Dumbledore's mouth:
"It is our choices, Harry, that show what we truly are, far more than our abilities" ~Harry Potter and the Chamber of Secrets
So, our choices matter, they have consequences. Voldemorts choices happened to bring his own downfall, he is the one responsible, not some foggy prophecy. He pushed Lily beyond her limits, and she made her ultimate sacrifice, creating Voldemort's enemy.
After all, if you choose to kill people chances are that they'll try to kill you back and eventually succeed (live by the sword, die by the sword, what goes around comes around, etc.)
Of course not. Had he decided to leave the Potters alone, he wouldn't have made Harry his equal and his mortal enemy, but being a dark lord is a dangerous profession. Sooner or later he'd have pushed someone else hard enough and they'd have pushed back just as hard.
Voldemort's choices, that's what determined his fate. The names of the heroes aren't that important : Harry, Neville (whom Rowling called 'might-have-been') or another kid... Sooner or later Voldemort would have created a foe strong enough to bring him down.
In Harry Potter and the Half-Blood Prince, Dumbledore says:
"If Voldemort had never heard of the prophecy, would it have been fulfilled? Would it have meant anything? Of course not! Do you think that every prophecy in the Hall of Prophecy has been fulfilled?"
"But," said Harry, bewildered, "but last year, you said one of us would have to kill the other -"
"Harry, Harry, only because Voldemort made a grave error, and acted on Professor Trelawney's words! If Voldemort had never murdered your father, would he have imparted in you a furious desire for revenge? Of course not! If he had not forced your mother to die for you, would he have given you a magical protection he could not penetrate? Of course not, Harry! Don't you see? Voldemort himself created his worst enemy, just as tyrants everywhere do! Have you any idea how much tyrants fear the people they oppress? All of them realize that, one day, amongst their many victims, there is sure to be one who rises against them and strikes back! Voldemort is no different! (etc)
So in relying too much on the prophecy, he handed Harry some powerful tools, and made him the one would defeat him.
So it seems that if Voldemort had never heard the prophecy, he would have survived that night.
Delphi's last plan to save her father was to just prevent him from heading to the Potters that night. She was under the impression that that would save him.
So it seems as if
If he hadn't gone, he wouldn't have 'died' that night, and would probably have never been defeated.
Some Time-Travel Theory
There are roughly two ways in which prophecy and time-travel can work:
Novikov's self-consistency principle: There is only one self-consistent timeline, and anything you do in the past (or as a result of prophecy), was already part of the timeline in the first place. You cannot change the past, but you can affect it. In particular, you can retroactively be the cause of events you already know happened (creating a 'causal loop').
The Many Worlds interpretation of quantum mechanics: Any change you make in the past splits the timeline into two branches; one in which you made the change, and one in which you didn't. In this theory, you can travel back in time and cause events that are inconsistent with your native timeline.
The Main Books
The main series of Harry Potter books follow Novikov's principle. The time-turner events in Prisoner of Azkaban are an excellent example of this. Everything the heroes see and hear their first time around is consistent with their actions and observations in the second iteration. In particular, future-Harry creates a causal loop by saving past-Harry's life.
The prophecy also fits this theory. Voldemort acts on it, unknowingly allowing it to come to pass: another causal loop. He did have some choice in how to fulfill the prophecy, because until he marked Harry as his equal, Neville fit the description too.
But Voldemort could not have ignored the prophecy. Don't misunderstand: the prophecy didn't magically compel him or anything. He still acted on it by his own free will. But in any universe in which Voldemort had it in him to ignore such a prophecy, the prophecy would not have been made in the first place.
If this recent screenplay is to be considered canon, that throws Novikov's self-consistency principle out the window. It comes closer to the Many Worlds theory, but it violates some of its rules, too. Sloppy writing, in other words, and what a shame after such a well-crafted series.
In this expanded canon, the closest answer to your question is yes. But really, because it doesn't adhere to any consistent set of time-travel rules, the answer probably depends on what would make for the best story.
Yes he would have been more successful as it was the prophecy that lead him to the Potters ( why not Longbottoms) and forced him to cast the deathly spell on the little Harry... If there would have been a case where he would not listen to the prophecy he would have been alive!
But it is a scenario where it shows that even when people are at the top of their game there is a slight fear in them and this slight fear leads to bad decisions as in this case made by Voldemort!
Kudos!
