Over the years I've managed to buy some extremely un-soapy soaps. Such things often appear at Christmas time with fancy makers names, fancy labels, and in fancy bottles. The unwary pay top prices for such things and hand them out to all and sundry as 'extra special presents'. I suspect we all have some of those at the back of the bathroom cupboard.
Personally I don't like BARS of soap, although I have a friend who always asks me to buy her several bars of 'Lifeboy Soap' before returning to France. She claims that the smell reminds her of small boys being washed! (I didn't ask)
Soap, as we all know, performs its magic by reducing the surface tension of water, making both the water and the soap perform as desired.
I have been known to re-fill old soap dispensers with good quality, lemon scented, Fairy Liquid washing-up liquid, but Lady M calls me an old skinflint. She, herself, would never buy anything but the best; by which she probably means the most expensive. But, whatever floats your boat! (N.B. I should mention here that Jean Shrimpton once told me that she used Fairy Liquid to wash her hair)
So, which soap is the soapiest? Without question it is the pukka liquid Savon de Marseille. Not those cheap imitations, but the real thing. I have three different liquid soaps on the go at present in our bathroom, and there is no question that the one above is by far the best. It is actually a PLEASURE to use.
Marseille soaps are traditionally made by combining Olive Oil with Mediterranean Sea water and a plant-based alkaline ash. The resulting soap was traditionally formed into large (attractive looking) 4 inch cubes, stamped with the makers names. Personally, I find these big solid lumps of soap unwieldy and annoying, so I stick to the liquid.
Life is too short to buy 'Macron et de Gaulle' savvon du Marsay (made in Taiwan); always go for the best, 'Made in Marseille'.