The story is quite trivial most of the time; it gets somewhat good during the last 25 or so eps, but it's not worth watching all those battles before it which don't relate to it any way. The few individual story arcs before that are extremely simplistic, if not nonexistent. Mainly you get the feelling that the author came up with them in 5 seconds in order to give some cause for the action.
It's a series from the early 90's, so the art isn't very cool. You'd think that when the series is just pointless action, they'd at least make the action look good? Well, you're wrong. They've not used even those flash and sketcy-line techniques they used on Dragonball at roughly the same time period.
There's no musical scores you'd afterwards. Unlike some people, I find several anime series to have music you want to listen discretely from watching the series. But YYH is definitely not one of those, so it's music is well below average.
The main characters are, besides Kurama, unsympathetic slow-witted tough guys. The bad guys mostly lack any personality, their motive to attack the main cast is mainly just because they're bad, and you forget them immediately after they get slaughtered - the shaggy story arcs mostly don't intersect in any way, so you never hear anything about them from any character (and if you ask me, that's one of the defining marks of a bad series). Some of the characters develop at the end - but again, it's nothing exceptional, and just goddamn not worth watching those never-ending mindless bloodbath battles!
So, the battles are long and dull, with exceptionally random power-ups or mutations. There's no adventuring, just tournaments or premised quests to go to some place to beat up some guys. There's little drama, and most characters remain one-dimensional. Unlike in Hunter x Hunter, the superpowers are pure raw power without any strategical element to them. There are only few fighting female characters, most are just cheergals. To me, there wasn't simply anything enjoyable or inspiring in anything.
Overall, it's not the worst series out there (to me the worst are those that try to be something but fail epicly), it just doesn't have anything to say. It's the most generic, mediocre shounen action series probably ever made, and you could watch it if you have absolutely nothing else to do, but don't expect anything.
If you want to watch a fighting series, watch Dragonball - there's some meaning to the fights, there's some plot in between them, and the action is mostly cool.
If you want to watch a quality shounen series which revolves around sympathetic and unforgettable characters, which is mainly adventure and not tournament, which has a good plot and only short battles right on the hot spots of the plot, or want to have a glimpse of that genius of Yoshihiro Togashi they talk out there, watch Hunter x Hunter.
Naruto is fine too.
