Played all three, and i gotta say it's a tough call, none of them are near SCV though, obviously, but between these three, hate to say it, but CaS's first entry was the best out of three.
Broken Destiny did good, more voice options, more face options, more options overall over SCIV, however you couldn't change body mass or size, and some things did not transfer well over to Broken Desinty, like Nightmares SCII helm, that thing was horrible.
SCIII beats SCIV and SC:BD strictly because it had more facial options and hair style options, other then old ugly dudes and white guys, it had Asian, black, and others, was versatile unlike IV, SCIII had quite a lot of Final Fantasy VII and Final Fantasy X hairstyles as well... but then again vocal pitch or tone wasn't selectable at the time... pfft, but then again SCIII does have overall more gear then SCIV. but if were talking strictly CaS and ignoring HD Graphics vs PS2 graphics...
My opinion is... SCIII > SCIV > Broken Destiny.
Thankfully SCV blows them all out of the water though, because it has everything past games had and then some.