Arye Gross voiced adult Kevin in the original broadcast of The Wonder Years pilot. That first airing followed Super Bowl XXII on January 31, 1988, and used Gross for the adult narration.
The pilot was later re-aired with the narration re-recorded by Daniel Stern. Stern became the familiar voice of adult Kevin and narrated the series' regular run, which is why many viewers remember him as the narrator from the beginning.
This creates a common mix-up: Daniel Stern is the canonical series narrator, but Arye Gross is the correct answer when the question specifies the original broadcast of the pilot. Gross's version was only heard on that initial telecast, making the wording important.