At a guess, I'd say all the people that had already bought 7 & 8 decided to take advantage of the recent sale to grab 9 for $1.49....

The current bestsellers list is pretty crazy, it's changing all the time. Either LOTS of people are buying, or very few are (which would be bad)

Is the bestseller list really based purely on sales? Or does GOG also favour titles it would like to sell more of?

Based on what I know...it's purely based on the best recent sellers

People kept their original copies of 7 and tossed Ascension? Now they're buying it again because its on sale?

Is Ultima 9 still worth a try despite how "ahem" terrible it is?

During sales people might tend to buy the games of which they where not certain so far, rather than those which they always wanted.

The bestseller list on the frontpage represents only the last weeks while by using the catalog page you get the all-time bestsellers. There Ultima 9 is on the last spot, so I would say the assumption is right that many people used the 75% off sale to get also the unholy one to complete the series ;-)

It is not terrible, just disappointing. See it as its own separate entity, not an Ultima game, and it can be enjoyable.

I'm guessing people thought it was worth playing $1.50 for, considering the amount of extras that come with it

I bought ultima 7 and 9 and included them in the same gift.

I don't know if whoever received it considers a gift, or a curse, but I sure as hell feel my life has been completed.

To be honest, I wouldn't even unpack it xD
Still too horrified about the Spoony review of Ultima 9 ("What's a paladin?" "Your knowledge of the land shall be great")...plus if there's part 7 and part 9, why no 8? Although Spoony lashed on that one pretty hard too. Anyway, it seems to me I should've played those games when they were fresh. I haven't played any of the Ultimas and today, I find it very hard to find them interesting based on what I've seen and read. Haven't even taken the Ultima games GOG is offering for free. They just look utterly unappealing to me, all of them, and while they might be RPG pioneer games, to me they look like time hasn't been kind to them. Sorry if this upsets anyone, just felt like coming clean with this.

Basically what AFnord said, as an action-adventure game released in 1999 it's fine, had a 3D graphics engine with physics which was revolutionary at the time. But as an Ultima game, it is an abomination.