Did Ging Really Say “You Should Enjoy the Little Detours to the Fullest”?
Yes. It is the last line of the 2011 Hunter × Hunter anime, Ging to Gon. The wording everyone shares is the fansub's; Wikiquote's transcript reads "enjoy the side trips, a lot, okay?" Same line, two English versions, and it is often filed under Killua.
Spoilers throughout. This page assumes you have finished the series.
Yes. Ging Freecss says it to Gon in the final episode of the 2011 Hunter × Hunter anime, and it is the line the series ends on. What people share is one translation of it; the transcript on the record is another. And it is quite often credited to Killua, who is nowhere near the scene.
The verdict
Real, but the translations differ. Wikiquote's Hunter × Hunter page records the closing line of the series, at the top of the World Tree, in this wording: "Enjoy the side trips. A lot, okay? Things that are more important than what you're hunting for could be right there by the side of the road." The version on every poster, "you should enjoy the little detours to the fullest, because that's where you'll find the things more important than what you want," is the fansub rendering of the same Japanese, which reached most of the English-speaking audience first and has stayed the quotable one. Neither is wrong. The transcript's "side trips" and the fansub's "little detours" are two translators' choices for the same word.
Who says it, and who gets credited
Ging, to his son, at the end of a story that has been about finding him. That is what makes it land: the father who abandoned the boy is telling him the search was the point. The internet's most common misfiling is Killua, partly because Killua is the more beloved character and partly because a well-known Tumblr quote blog carried his name in its address while posting the line; some listicles of "Killua quotes" include it with Ging's name still attached, which is how a reader skimming headings ends up thinking Killua said it. He did not. Wikiquote has no Killua lines at all, which is a separate problem for a site that wants to quote him, and is not evidence about this one.
Why the fansub wording won
The 2011 series finished in 2014, and the fansubs were what English viewers watched week to week; the licensed release and its transcript came later, by which time the "little detours" wording had been put on ten thousand images. This is the same pattern as Itachi's speech about reality and Gojo's "nah, I'd win": the fan version arrives first, the official version arrives correct, and the one people remember is the first one. For a line whose whole meaning is that detours matter more than the destination, there is something fitting about it having two routes into English.
What to quote
Either, as long as you say which. The fansub wording is the one your reader will recognise; the transcript wording is the one you can point to. Hunter × Hunter does not yet have a quote hub on this site, because Wikiquote's page for it is thin and every character needs two sourced lines before a page exists; when it opens, this is the first line that will be on it.
How we checked
The verification process asks for a primary or editorial source; the primary one, Wikiquote's episode-numbered transcript, supplies the scene, the speaker and the official-side wording, and the fansub version's ubiquity supplies the rest. The entry in the fact-check database is real with the translation caveat, and with the note that whoever is on the image, the speaker is Ging.