- This page is a matter of opinion due to lack of (credible) references aside from 10 years of personal experience.
CD is not good enough. It can not record sound below 20 Hz or above 20KHz. Also, 16 bits is not enough resolution to fool human ears. 24/96 seems to do the trick. I am a few decades old and I can still hear to about 22 KHz.  This is beside the point. The high frequencies are where ALL of the imaging comes from. The level of perfection of their synchronicity determines how perfect the stereo image will be.
To paraphrase my comment from a reddit post:Edit
Time and time again I've heard fantastic CD upsampling from such companies as Arcam, DCS, Esoteric, etc. that made CD's sound almost identical to their SACD counterparts. In some cases the upsampling was to higher-res PCM. In others it was to DSD. Whether PCM or DSD the results were clear. The CD's usually sounded almost as good, and sometimes indistinguishable from their hi-res counterparts. What this means is that 16/44.1 is NOT good enough. The most telling example is cymbols. They sound very harsh and don't have nearly enough decay with CD quality. After upsampling they sound real and smooth. I'd say for the past 10 years it has been very easy to find an affordable CD player with fantastic upsampling built in. Don't replace your CD collection just yet, especially if you've gone through the trouble to find great masters like from Mobile Fidelity, (the country of) Japan, or the (country of) U.K. Instead buy a great upsampling DAC.
Even better is to get a DAC that both accepts hi-res input AND upsamples lower res input. Naturally that's what most audiophiles are doing these days.
The video analogyEdit
When HDTV's started selling there was almost no HD content at all. (I remember Unity Motion broadcasting snowboarding and "Earth Girls are Easy" over and over again.) The TV's had a benefit though. They would upsample regular conent into HD content before displaying it on their screen. We could all still see the difference in both detail, color depth, and contrast ratio. Over the years upsampling has made leaps and bounds, but it's still not convincing (unless you own a Faroudja). The moral of the story is that the exact same thing applies to audio. It's very difficult or impossible to recreate original information that has been thrown out. We (humans) have a natural tendency to easily believe things we see, yet are very skeptical of things we hear.
 if you claim you can't hear the difference between Cd and hi-res, or speaker cable, etc. and so forth AND you truly have tried on a poper system, then you probably have hearing problems.