By that I specifically mean dungeon crawlers whose dungeons are pre-rendered.

The only other game I know of is Anvil Of Dawn. I've looked around the web for mention of other dungeon-crawler games that use similar technology to Stonekeep and AOD's, but I haven't had luck. Are these really the only two?

I'm not sure what you mean by pre-rendered. Do you mean the fact that moving between squares or turning is actually animated (as opposed to, say, the early Might and Magic games where it's just an instant jump)?

If you haven't already, you might check out Legend of Grimrock, which is a very recent take on the genre. It's available here on GOG and has some very pretty 3D graphics, and is of course fully animated.

You might also take a look at the Ultima Underworld games here on GOG. Those are fully 3D and fully animated, although they are NOT grid-based like Grimrock and Stonekeep. So you have full first-person movement in those games.

I also know a lot of older grid-based games that were not fully animated, but it sounds like those aren't what you're looking for.

The graphics in Legend of Grimrock and Ultima Underworld are rendered in realtime. Also, Might & Magic (as well as Wizardry, Ultima, etc) draws bits of the environment in chunks of hand-drawn sprites, from furthest to closest, making it somewhat... I'm not sure what exact word I want to use, but you could theoretically edit the dungeons in an editor and it'll display fine in-game without any extra work done on the art assets to do so.

By contrast, the impression I get from Stonekeep's and AOD's environments is that their environments were pre-rendered in a 3D program (like how The 7th Guest was done), and then extra programming magic was done to still draw real-time things properly (like enemies, items that are thrown, NPCs other movable entities) so that they appear behind the solid objects in the 3D renderings.

At least, this is the impression I get. If Stonekeep's (and Anvil of Dawn's) environments aren't pre-rendered, then I'm even more impressed that it fooled me into thinking they were.

OK, I see what you mean now. That's a pretty specific criterion! Sadly I don't know of other games that use that exact method for their graphics. I do think that in Stonekeep the real-time elements were done using sprites and FMV. Walls were pre-rendered but other objects like tables were sprites and enemies were FMV, so it was easy to have enemies appear to be behind objects. Someone correct me if I'm wrong about that though.

If you want to consider similar games, but ones that move you around instantly, (ie. when you turn, you don't see the walls rotate, you're simply facing the new direction right away) I'd suggest:
Eye of the Beholder series (especially 2).
Dungeon Master series (Grimrock is similar).
Lands of Lore 1.

That's all that come to mind, anyway.