Does the version of Zork: Grand Inquisitor sold here have DVD-quality videos? I see that Wing Commander 4 and Legacy of Time here do have that, but no such mention with Grand Inquisitor.

No, the videos on Grand Inquisitor are very poor quality, as are the graphics for the entire game. I remember loving this game when it first came out but, sadly, it hasn't held up, IMO.

I doubt i'll even bother finishing it as the graphics are so bad :(

There is a DVD version with much better video quality, But gog didn't use it because it requires to much work :(

If you are really interested in playing the enhanced version, I could explain how. FIrst of all you need to find it on ebay, though.