So to put short and sweet, I love this game. Rhythm Heaven Fever has so much charm put into it, it's nearly impossible to dislike this unless you are very bad at rhythm games. I, personally, can be considered above average at them, having a lot of musical experience myself.
First of all, the art style. Yes, it is admittedly very simple, but that's what makes it so memorable. With the bold outlines, the colorful characters and background, it's definitely the most polished and clean title of the franchise.
Obviously, there can't be a rhythm game without its music, and holy shit it slaps, it has that groove, while also being extremely catchy, and even though it's repetitive in nature, not only does it have to be for the gameplay, it doesn't get annoying even when listening to it alone.
The game is so witty, it creates these ridiculous scenarios that never really fail to disappoint. I know I'm repeating this but it's charming, and it also feeds into its gameplay.
It's also fairly challenging, it is simple, and the rhythms are not the hardest, but the timing can be a bit frustrating sometimes, which is arguably my biggest flaw with this game, but it's fun to see other people fail.
I do have a few nitpicks, the controls aren't perfect, and it can be obnoxious, I wish they would shake up the gameplay a bit because, at its core, it's fundamentally the same game as the rest of the titles.
But who cares, I think it's better than the original by a whole lot, haven't played Megamix or the first one (I forgot what it's called), but this is one of my favorite rhythm games of all time. I'm glad to see that it's actually had a resurgence over these past few years.
8.5/10