I'd say, "natural ability". If someone has it he doesn't have to put in nearly as much effort to accomplish something; and if he decides to put in some extra effort he's likely to REALLY accomplish his aims or create/produce something that is excellent. While sometimes a person with natural ability can achieve excellence without much effort at all, sometimes it takes plenty of effort, as well as natural ability. Still, the person with natural ability who is willing to put any effort he needs to has a head start.
People like to believe that effort is the more important thing; but without natural ability (at least that's related to any specific goal), it can take a whole lot more effort to achieve what one wants to achieve; and sometimes lack of natural ability can be such an issue the person can have particular difficulty achieving real excellence. I'm not saying the person without ability can't work very hard and achieve excellent, but it's far more challenging.
If you achieve something without having to struggle to do it - I see that as being fortunate; and I don't think natural ability should ever be under-valued. There's a reason we often hear, "S/he's a natural." (When it comes down to it, even if a person doesn't want to accomplish a particular thing, it's always just handier to have natural ability that, often, comes in handy in areas not related to a particular task.