7 is one of the best of the Ultima series, and IMO Serpent Isle (7 Part 2) is not only the best Ultima, but still one of the best CRPGs made even now.

8 is decent in plot and gameplay (particularly with the post-release patch that alleviates the quirky jumping mechanics of the original version) but is frequently felt to not live up as well to its lofty series label. An expansion was planned but never released (at least one prototype retail box was built, however, which is one of the most valuable of all Ultima collectibles)

9 was basically rushed out the door incomplete, and even the post-release patches only go so far to repair this. It's not Big Rigs: Over the Road Racing incomplete, but you can very readily tell that it should have had considerably more content, and bugs are copious. It's not a totally unenjoyable game (had it not been an Ultima, it might not be much worse than a lot of AAA titles end up being at release, and I found it considerably more enjoyable than, in particular, Ultima 2), but it does not live up to the level that the conclusion to the Trilogy of Trilogies deserved.

Ultima 7 made its world feel rich and alive in a way that many modern games still don't. It's a joy just to explore and interact with things. Combat is something of an afterthought, but at least you can get it over with quickly if you don't enjoy it. Serpent Isle is similar, but the story was obviously gutted in the latter half to get it out the door.

Ultima 8 had an interesting setting and plot in the works, but neither were sufficiently fleshed out and the gameplay was atrocious. The combat managed to be worse than 7's because it was needlessly prolonged. This led many players to just run past every enemy they encountered, and the game actually permits this.

Ultima 9 was just a trainwreck, and it was only through the amazing dedication of the fanbase that it became remotely playable with unofficial patches. They refused to let the series end on such a bomb.

Huh - all this time I thought IV (and V) were the pinnacle.

Thanks guys, I'll be looking forward to VII.