Poor Ultima IX. So many good little details that utterly failed to come together into a satisfying whole.
I still maintain that (post patch) Ultima VIII was a pretty good game. It was just a bad Ultima. If they'd leaned into the action-y elements a little more and made it a side-game like the two Underworlds I think it would be remembered fondly.
I think that Ultimas I - VI could actually all be remade as one large unified game. The different threats to Sosaria/Britannia would all be happening simultaneously in different sections of the world, and don't necessarily need to be completed in a particular order. Overall, the game would basically be a spiritual remake of Ultima IV, it's just that the virtues (which probably need to be tweaked a little) tie more directly into the to the various re-imagined threats from the other games; what happens isn't as important as how it happens.