We get uncolorable parts regardless of the number of color slots. Take @
Zaden's hated Menghu Curiass...3-4 colors, only one slot that can be changed. Many other parts have fewer than 4 slots that you can edit, and portions you just can't. Aggravating sure, though sometimes is a fun challenge.
On topic: I would rank them V>III>IV; no comment on BD since I never had it or played it.
I agree with this ranking. III was very unique in it's design, which is interesting considering it was their first attempt in the series. It had superior options such as the best system for facial hair, and no equipment conflicts, which they painfully added in IV. If the equipment is going to clip, let it happen and let the players decide if it looks good or not.
At first, the skill points in SCIV's Creation seem annoying, but you can have separate creations, some for looks and others for skill points. The reason IV's was the worst was because they took out some good features that were in III, and other than that it's basically the same as V with less options, thus limiting your creativity.
V, however, tops the charts with its limitless customizability caused by the addition of many more sliders for your character's body, 3 fully adjustable equipment slots, and the ability to add stickers, patterns, and even edit the color of your weapon.
In all games, the voice options have been lame, but we can hope for better options in the future and be glad that we have such awesome tools to work with so far in V. Hopefully, if there are very few voice options, they will at least add the option to make them mute/Voldo-ish if you don't like any of the available options.