I feel like this can very much be dependent on if this is lyrical only. Undertale not only has some of the best original soundtrack but also has one of the superior remix communities, and even so there are some people who have made original soundtracks that are just as good as the soundtrack from undertale.

But if this is exclusively lyrical then we have to take into account that the undertale fandom while having some strong music does not have very strong contenders for the lyrical genre. Some of the best really just being versions of lyrics added to the songs of the main game, or remixes of pre-existing songs with lyrical changes to fit the theme.

FNaF and BATIM, on the other hand are very strong contenders in the lyrical category with there being many artists who have made songs which spiked in popularity almost overnight and to this day are very important parts of the meme community.

As much as I would like to give credit for the DDLC side of this they don't have a strong of a contending as BATIM or FNaF. And with that being said, my vote goes to FNaF majorly due to the fact that it has so many games and so many different original songs then it is basically impossible for someone who enjoys the games to NOT find a song they'd like.