4, 6 and what I’ve read of 7 are all tied for me! Followed by 2, 3 and then 1. Haven’t read 5.
4 might be my sentimental favorite of the series, the first time I thought Araki nailed a solid bench of side characters. Kira is terrifying as well. 6 had relatively tight storytelling and some ridiculous high-concept stands, 7 is maybe the most polished Jojo arc I’ve seen up to the point where I stopped? 2 is a lot of fun but the series didn’t really mature until 3, which still has a few too many stand-of-the-week chapters. 1 is rough but had some wild moments I suppose. As for favorite Jojo…Jolyne maybe???