Ah, let's see...
In your own words, what is a visual novel?
An art medium that combines literature, illustrations, and music. The ratio of each of those three in a given VN depends on the work itself - some are more reliant on the music (Higurashi, Umineko), others don't have a lot of graphics (Narcissu). A visual novel may also feature interactive elements; if it does, it could even be considered a video game (Phoenix Wright, Sengoku Rance). I'm not exactly sure where the line between the two is drawn, though I'd like to figure it out someday.
What makes you love VNs?
Hmm... I'm not exactly sure, to be honest. I suppose, in one part, the ways the stories are constructed - their length, the first-person narrative style, choices, stuff like that. I also enjoy more depressing or darker stories, and those are plentiful in VNs. (and I like manga-style illustrations too lol)
On the other hand, something that I never noticed until I read an article that Aaeru linked to somewhere - visual novels are like regular novels in that they allow the reader to use their imagination to form the story... but while in regular novels, you don't get any sort of guildelines regarding that, VNs lay down a framework that you can base the scenario off of using the visuals.
I'm not sure if I worded that properly, so here's an example that I took from my own experiences. Whenever I'm reading a book, I often find myself imagining what a character or place looks like as soon as they're first introduced, only to have to redo that mental image once the character/place actually is described. I never have such problems with VNs, since you can already see what everything looks like as soon as they appear, but those visuals are only there so you can have an idea of what's going on - enough to construct the mental images without confusion.
Name one favorite song from a VN:
Eh, there's one from Umineko that I always thought of as really amazing, but I don't remember its name and saying when it plays would probably be spoilers. Though most songs from Umineko are excellent, really.
Can you think of a moment in a VN-to-Anime where the anime effectively mirrored or embodied the novel?
Huh... I haven't watched any good such adaptations to comment on this (well, I'm watching Steins;Gate right now, but I haven't read the VN). However, having watched the Fate/stay night anime after reading the original work, and having found it amazingly terrible, I'd like to present my opinions on why it failed so hard.
• The most immediate error that was apparent to me while I was watching it was, without doubt, their failure to stick to a single route. It seems that they decided to started off with Fate, but then tried to shoehorn elements from Unlimited Blade Works and Heaven's Feel into the plot, only to realize that it wasn't working out as they neared the end.
Considering that F/sn has a pretty serious story, the clusterfuck that this resulted in should be apparent. Story elements that were completely irrelevant to Fate's plot ended up being introduced but not fully developed, which just made things confusing (example: revealing Archer's Noble Phantasm, but not his identity).
• Second... ok, obviously they couldn't animate the h-scenes since the anime aired on TV, and the ones in the VN were pretty bad anyway, but... couldn't they have taken the scenes from Realta Nua (the non-h rerelease) instead of making shit up, like the infamous Mana Transfer Dragon? (and let's not even mention the Mana Transfer Dolphins from the UBW movie)
• Third... ok, bias here, but I just don't like Deen. The quality of their works is pretty... ehhhhh. F/sn is one of the most famous visual novels out there, so why did such a studio get to produce its anime? Same goes for Tsukihime, whose anime is also famous for being horrible (I haven't watched it yet, though, so no comments on it). I rejoiced greatly upon hearing that Ufotable would be producing Fate/zero.
Anyway, I'll refrain from bitching much further about this. Bottom line, not being completely faithful to the original work, not being able to decide which route to do, having a shitty studio produce the anime. There's probably more to this, but that's what I can think of right now...
I think I'll add a "what I think would make an adaptation be good" section to this tomorrow, so as to not make this part so bitchy lol.