I should probably start with this to get a few answers I know are coming my way right out of the equation altogether: 

1. No, this isn't the age-old question of "If *you* could have superpowers...?" but just asking a general question of the single greatest ability for ANYONE to possess.
2. No, you can't say "Omnipotence" or "Omniscience" or Omnipresence" or "Omni-" anything; that's cheating. Obviously. Also, no Magic--it's too broad a concept, and covers far too much room to classify effectively, and it's kinda invalidated in worlds where EVERYONE has Magic since it's never treated like a superpower in those type of settings.
3. This is a singular power, and we're going to be taking this in a vacuum and assuming that this singular power, in possession by a random person or other sentient corporeal being, exists exclusively on its own, which takes out all abilities that grant/revoke/boost/weaken/steal/drain/reverse/manipulate/etc. other superpowers.

Here's the groundwork: How would you decide what the best possible superpower is? 

* Is it by the scale your power can reach (affecting everyone in a large city to encompassing entire planets, and even further than that)?
* The amount of influence your power has/is capable of changing (like, teleporting from your house to the other side of the planet in the blink of an eye)?
* Is it about the capability it has to destroy? To create? To repair?
* The learning curve needed to fully utilize and master it (I'd think superhuman strength would be a lot easier to just pick up and learn as opposed to gaining the power to rewrite all of reality down to a subatomic level)?
* How well it can be used in a fight (like pyrokinesis)? How well it can be used OUT of any confrontation (like super speed), or even how well you can avoid any type of conflict period (like invisibility)?
* Maybe it's the versatility of how the power can be applied (like telekinesis; you could grab things just out of your reach, manipulate multiple objects at a time, perform surgery, and even flip cars with enough practice)?
* What about the amount of change created in proximity to the amount of effort output (like waving your hand to cause a house to explode or reducing someone to ashes just by touching them; extremely minimal effort into big change)?

What is the determining factor that would go into deciding what the "Best [Single] Superpower" would be? The one ability that would almost completely invalidate all other superpowers; if not completely unstoppable, then at the very least not easily overcome or very difficult to counter against without careful planning.

TL;DR version: What's the best superpower, and why would be considered THE greatest/most useful/most helpful superpower?