Underworld developer here. We certainly started it before we got the deal with Origin, but a lot of the design was done afterwards with the fact that it was an Ultima in mind. I'll grant that its Ultima-ness was thinner compared to many of the games with Roman numerals on them.
Ultima Underworld II, of course, was designed to be an Ultima game from the start.
I've always felt that UW1 is massively underappreciated for the impact it had on computer gaming. It's been attested that John Carmack was inspired to create the engine that would eventually become Wolfenstein after seeing Underworld at a 1990 software convention and saying that he could write a faster texture mapped engine.
It had an enormous impact on me as a child discovering games in the mid 90s. I got a copy of UW on a games CD I got bundled with a Creative Soundcard[0]. This also came with so many other fantastic games, of which another was Ultima VII.
By the way, the most ingenious thing UW did was its acrobatics mechanics, when you subtly could jump for longer and longer distances, and I didn't even realize that it was increasing up until I restarted the game and suddenly found out that I can't make a rather casual jump over some chasm, which could be easily jumped over in previous save. I don't think I ever saw such things in other games, only some platformers have shown something resembling that.
Just so you know those games were badass! I had so much fun playing them. Elder Scrolls came out later and that was the first fantasy FPS game that I has as much fun with as underworld.
