I think we're long overdue for some stupid, poorly applied fandom math performed by someone who barely scraped through her college math courses with her dignity intact. And since I really haven't been generous enough with Xellos over the last year to update
his success rate, it's time to look at something else.
I was looking through Fanfiction.net's filter feature to see how different Slayers pairings stacked up in regards to fic amounts/types. Here's what I found:
Pairing - Total # of Romance Fics - # & % of Completed Fics - # & % of Mature Rated Fics
Xellos/Filia: 207; Completed: 122 (59%); Mature: 12 (6%)
Zelgadis/Amelia: 172; Completed 115 (67%); Mature: 23 (13%)
Lina/Gourry: 160; Completed: 106 (66%); Mature: 28 (18%)
Xellos/Lina: 111; Completed 67 (60%); Mature: 20 (18%)
Zelgadis/Lina: 107; Completed: 66 (62%); Mature: 10 (9%)
Xellos/Zelgadis: 67; Completed: 50 (75%) Mature: 31 (46%)
The results are interesting. Xellos/Filia has the most fics, which is an impression I've always gotten about the pair. It's particularly intriguing since I do not think that dynamic works out in nearly the same way when you get to fanart, which would mean there's something about the pairing that specifically appeals to authors. Also interesting since one of the components of this pair is a one season character, whereas all the other pairs are made up of multi-season characters. Shows that Filia and Xellos/Filia made a strong impression even despite the limited episodes in which the pair could be explored. Xellos/Zelgadis had the fewest amount of fics (that I thought was significant enough to dissect on this list. There are obviously pairings with much fewer) on this list but the largest proportion of completed fics and, by a very wide margin, mature rated fics. The latter statistic might have been brought about for--and I'm going to use a technical phrase here--reasons of sexy. Whereas Xellos/Filia, with the current largest amount of romance fics, has the smallest percentage of mature rated fics on this list. A bit odd that we're coming out the prudes on this list considering our avowed approval of demon-on-dragon relations, don't you think?
P.S. There's limits to the accuracy of this little sampling since it only looks at Fanfiction.net fics; if more than two characters are specified for a romance fic it can come up in one of these characters even if it's not for that pair; it doesn't account for secondary pairs; it doesn't account for fics with pairing affiliations that aren't romances. Nevertheless, I think this is a good way to get a thumbnail sketch of the dynamics here.
P.P.S. Sorry if I fucked up on any of the math or made a mistake with the filtering (that kept happening, but I *think* I've fixed things).