I've listened through the samples again, and I'm warming to elements of it.
With Doom and Duke, it's really only the guitars that are rubbing me wrong.
With ROTT, it's kind of everything. There's a lot of inherently cheesy sounds in this composition, and older modules just pull it off in a much more cohesive fashion. https://www.youtube.com/watch?v=6erC93RvZeI
I've said my bit on Star Wars. I don't think it sounds good on any MIDI device, and the V3 doesn't change that. That's not the V3's fault.
Warcraft 2 - I think this sounds spectacular, personally.
Settlers 2 - As Warcraft shows, the V3's potential for orchestral stuff is big. But this one falls over in a few places. The opening flute melody is too understated, lacking attack or something. The xylophone (I think) at about 0:26 seems to come in an octave low. Overall it's coming off a little soft and not really working compared to https://www.youtube.com/watch?v=qZguUBX9b_E
It feels like a great bank could be crafted out of these sounds, but I have no idea what that process involves.
[edit]
Is there a definitive list of games with true GS support? Not looking to start lists in this thread - surely there is a thread or page somewhere, but my searches aren't turning one up. MobyGames has a category but I'm not sure it's reliable (apparently it just lists games with Sound Canvas in the options, which doesn't necessarily confirm GS functionality).