Followed your instructions to the letter, but only Ultima I and Ultima IV work correctly (it may be worth noting that I'm also playing them all patched with Pix's Ultima Patcher, which automatically applies all the fan-made patches to the GOG versions of the games, like the Ultima IV VGA Graphics Patch). Here's a log of what happens when I try to run all of them:
I: Works fine.
II: Stupidly fast (when I try to use the launcher's built in MoSlo, it says the OS "denied access to the specified file"), and when I try to create a character it gives me the "not a blank player disk" screen.
III: DOSBox Opens, then immediately closes.
IV: Works fine.
V: Divide by 0 error.
VI: "Drive C is mounted as local directory" and then nothing happens.
VII: DOSBox opens, flashes a bit, then closes.
VII Part 2: Opening cinematic plays, then it closes.
VIII: DOSBox opens, then immediately closes.
Underworld: DOSBox opens, then immediately closes.
Underworld II: DOSBox opens, then immediately closes.
The Savage Empire: DOSBox opens, then immediately closes.
Martian Dreams: DOSBox opens, then immediately closes.
Well then... lets get some info and we can start debugging and posting fixes shall we?
Ultima Trilogy is installed to "C:\Program Files (x86)\GOG.com\Ultima Trilogy", I assume, for the simple fact that Ultima I works for you.
I applied the patches using Pix's patcher as well so I could test them and U3 crashed on me, but everything else worked perfectly.* As for U3 crashing, I have an idea as to what's causing that but I don't have time to look into it right this second.
Let me know where the rest of your games are installed (I know you said it's the default, and I believe you, I just want to concretely rule out problems.) Also let me know where you put the config files and batch files.
I'll check back in the morning after I've tested my hypothesis on U3.
*Actually no, a lot of the games ran stupidly fast as you mentioned. I have ideas there too, and they're related to what I think is wrong with U3 (wrong file being called after applying the patches.)