I believe you're conflating the 50mm f/1.4 USM and the 50mm f/1.2 L II USM, which is confusing some folks. there's a vast price difference between the two.
if you're referring to the 50 f/1.4 USM, yes, at ~$350 US or so it's a great price for a great lens.
if you're referring to the 50 f/1.2 L II USM, at ~$1500 US or so it's probably not a best first-purchase lens unless you really know for sure it's what you want. even if you know a 50mm focal length and wide-open shooting is what you want, a lot of people still decide to go with the cheaper 50 f/1.4 USM instead.
The 50mm f/1.2L is not a "Mark II" lens, as the original 50mm "L" was f/1.0, not f/1.2. Perhaps the OP is actually referring to the 50mm f/1.8 II?
In any case, as others have stated both the 50mm f/1.4 and the 40mm f/2.8 Pancake are both good lenses; I would definitely choose the 40mm over the plastic 50mm f/1.8 II. If you don't need to shoot wide open, then the 40mm might be a better buy over the 50mm f/1.4, especially since it's still on sale for $150 and because there's growing talk of a new 50mm coming this year.