They're all great, but Rondo is the one for me of these, and apparently for Konami as well since it's the one they followed up on. Bloodlines plays fine but has a thing for me where it feels too visually busy and the colors are too... not bright, but too colorful? Too saturated? Idk, but it detracts from the experience. Super IV is definitely well made, but it makes me sleepy? The slower pace and the music doesn't hit quite as hard as other titles. Also, the "but you can whip 8 ways" thing doesn't hold water for me, because that's why subweapons exist in the series. I've never been a "git gud" kind of person, but it's an unnecessary freedom, as evidenced by the way they've never revisited it.