I like expanded universe in general. I've always thought that novels were the way to go, I enjoyed the VII and XIII novels because you didn't really need them, but they helped fill in different points and expand characters.
I suppose it's all about quality. VII was shit in that regard, quality control was all over the place, and unlike XV which was designed with multimedia in mind, VII was a stand alone title that wasn't built upon until years after.
But I have a feeling that the multimedia thing is a trend going on in general. I've been keeping up with the anime charts as the disgusting weeb I am, and lately I feel like I've been seeing a lot of the "this anime is part of a multimedia project" pop up a lot (usually the trifecta of an anime and game and manga), many times the quality is merhurg and none are as expensive as FFXV.
I mean, Advent Children was a mild success within the fandom but Spirits Within nearly tanked them. And Advent Children didn't have Sean Fucking Bean. I do get worried whenever I see cgi movies pop out of games (ie Resident Evil and Tekken) because they aren't normally good (except for the second RE one) and can fuck them over if they aren't paying attention to their budget.
Also, I don't want a terrible cgi movie to be the thing that brings over big names like SEAN BEAN to games, we already have a bad rap.
But going back to the quality again, I feel like outside of the novels, which are almost always interesting because it's usually plain character development, everything else has been inconsistent. The XII manga was boring and ugly, and the Type-0 manga, as elusive as it is, is absolute horseshit, why would they even bother? I don't think I watched FFV's anime sequel so I can't comment on it. Spin off games are usually soulless, and it takes a prayer and a miracle to make them good, I liked CC, but BC was apparently bad and DoC is horrible. I hear bad things about After Years, and XIII's trilogy got mixed reviews (even if I liked them). XII's sequel is a bit hard to talk about because well, I didn't play it but it also is part of a larger franchise.
Other games are doing the multimedia thing too. And 99.9% of anime adaptations of games are absolute crap, I fear for the new Ace Attorney coming out this season. I feel like the best parallel would be maybe the Resident Evil cgi movies or the Tales of Vesperia movies, Vesperia movie apparently was great but I don't think the RE movies did anything really, even though the second one was actually bearable.
As far as the Ultimania goes, I'm fine with it. We don't get databooks in the US either, and I think it really is a Japanese specific phenomena, and just wish they would publish it in the US. The only thing it does is encourage people to rip out the pages to scan it, and overwork the fandom translators. :/