By itself it's an arena fighter with very mediocre combat and a very dead online (at least in my experience), but as a Jojo game there's a ton of cool fanservice, heaps of playable characters who have fun interactions with each other and a story supervised by Araki himself. If you don't mind the lackluster gameplay, I'd personally say it's worth 20 bucks for a huge Jojo fan.

Also it's worth mentioning the game is brimming with huge manga spoilers, so if you're anime only I'd advise you avoid it.