I've used both CMSS-3D and Dolby Headphones extensively (and listened to most of the others), and I don't believe it's worth the trade-offs in audio quality if you have good open headphones.
Virtual surround processing can change the sound somewhat, but I wouldn't say that the better systems degrade the audio quality.
Sound quality is not the main issue though - it's audio positioning.
One of the problems with stereo audio is that when you listen to it using headphones, sounds played in each ear are completely isolated from one another - whether you have open headphones or not.
One of the cues that our brains use to locate sounds is the time delay between when a sound hits one ear and then the other.
Headphones completely lose this without any audio processing, which puts the sound "inside your head" and can make things sound unnatural.
This is why a number of high-end headphone amplifiers include a "crossfeed" feature:
https://www.youtube.com/watch?v=0Rn3siX93fM
But crossfeed is not all that virtual surround does - it's only a part of it.
Adding crossfeed to a stereo signal is an improvement, but is still not as good as a device converting a 5.1/7.1 source to a binaural signal.
Processing 5.1/7.1 channels of information is a far cry from the direct API support of the past, where the game itself would directly report the coordinates of the sound (I believe 128 channels was the maximum at the time), and translate that down to binaural stereo.
The 5.1/7.1 approach however muddies the sound, and depending on the implementation can sometimes come across as being inside a cave or tin box. There is also no vertical information, limiting the virtual surround sound to the horizontal plane. If I had to pick though, I'd say CMSS-3D is the best one of those.
This is a false equivalency, since there is no vertical component to stereo sound either.
Stereo audio positions sounds along a horizontal line that goes right through the middle of your head when you're using headphones.
Surround sound positions audio in a flat 2D ring outside of your head.
3D audio can position sounds in a sphere around your head.
But outside of old PC games, and a handful of newer games (typically games built for VR) very few games use 3D audio.
The headphone audio that you get from the majority of games is a stereo sound mix.
So neither the stereo sound or virtual surround options are going to give you vertical positioning - but virtual surround gives you much better positional audio.
Stereo audio on a pair of headphones gives you very directional sound - that is to say, sounds will be very strongly pushed to either the left or right side of the headphones, and there is generally a point where a sound source flips from one ear to the other.
However that is not good
positional information. Good positional audio is being able to hear whether something is in front or behind you. At a 60° angle or a 30° angle from your current view. Not just very obviously pushed towards one of the channels.
And finally, there have been a few games recently which have implemented software-based virtual surround sound directly, which can obviously be used with whichever DAC you wish. A few that come to mind are Overwatch, Elite: Dangerous, Resident Evil 7, and VR games. Overwatch uses Dolby Atmos and Elite: Dangerous uses DTS Headphone:X. Both of these are object-based surround sound technologies, which means it can do what I mentioned previously of picking sound coordinates instead of only using 5.1/7.1 channels, and this obviously includes height information as well.
Yes, 3D audio is best and that's why I still have an old X-Fi card in my PC for CMSS-3D in supported games despite that being a pain to use on Windows 10.
But only a handful of games use 3D audio. The majority are only using stereo sound in their "headphone" mode - if they even have one.
