Ultima Underworld II, of course, was designed to be an Ultima game from the start.
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.