Up to four GOG games that will not go Full Screen on my laptop which only has a 1366x768 resolution.. Last two games were Disciples 2 and Etherlords 2 The games easily go Full Screen on my desktop which of course has higher rated resolutions.. Is there a persistent problem or an answer to this ??? Thanks...

Is it that they are only playable in a window or that there are black bars on the side?

As far back as late DOS times there have always been lots of games demanding a certain minimum resolution and that has not changed now.

Now, someone COULD make a GOG mix with games that work fine on 768 or even 600!!! pixels height.

I really hope you did not mean filling up the screen completly. I, for one, would rather have the black bars and keep aspect ratios than have things stretched. Wide monitors used to be scarce to the point where games were not made for their resolutions.

Some games wont run fullscreen properly (ie black bars at the sides / top). Disciples 1 did this on my screen (same res).
Other games may have an issue with the specific resolution. I found on occasion if a game won't launch / fit the screen properly, then setting my desktop resolution to 1360x768 can sometimes help.
I think in this case though, its just the specific case of the games having a black border. I'll check with disciples 2 and get back to you shortly.
Okay, just tested and disciples 1 seems to be locked to the original res regardless of desktopsettings, Disciples 2 on the other hand will stretch by applying "maintain aspect ratio" in the graphics card settings (these should be available by right clicking the desktop - at least they are for me).

Some games do just kick off if you have a non-standard 4:3 or 5:4 resolution and refuse to run. Total Overdose is one of these, but there's a third party widescreen patch that enables full support.

I feel your pain. In my case I don't really mind the windowed mode/black bars, it's the lateral stretch to widescreen that pisses me off. True for all games running in DOSBox and ScummVM, I end up playing those in windowed mode with 2x zoom. Recently had the same problem with BloodRayne 2, which was trickier, I ended up getting a widescreen patch but even then it had issues.