I can't really say which amount makes up a "perfect" multiball.
I like the TZ 3-ball multiball modes, but I also like the 6-ball Lost In The Zone.
I like playing supergame on Judge Dredd because it essentially starts out with multiball, and can progress during play.
I like Tron's stackable Quorra and Light Cycle modes, and the Quorra add-a-ball feature is the closest thing to a wizard mode during regular gameplay if you have the light cycle mode going at the same time.