On a purely entertainment level, it's a 10/10. It's the kind of thing that could have an absolutely terrible storyline but still be fun to watch because of the characters and the style. But JoJo actually has a good story overall. Story is 8/10 for me, so that's what i'll rate it. Individual part ratings:

Phantom Blood: 5.5/10 (didn't like it all too much) Battle Tendency: 7.5/10 (when JoJo started feeling more like the JoJo we love today) Stardust Crusaders: 8/10 (love this part, but it's unfortunately held back by some very poor pacing) Diamond is Unbreakable: 8.5/10 (my personal favourite part so far, I think Kira is a phenomenal antagonist) Golden Wind: 7.5/10 (should be noted I read the manga for this part, I didn't watch the anime. Probably one of the most purely entertaining parts) Stone Ocean: 9/10 (Favourite part so far, both in the anime and the manga. Yes I finished the stone ocean manga as well)