Music is a draw. Villains, maybe also a draw? Lavos is a boring villain, but CT does have Queen Zeal, Magus, Dalton, etc. So it comes down to side content, which CT wins easily. Does Undertale have much side content? Do we count going for the genocide route or talking to various people as a side content? CT has so many great side quests that I feel it has some of the best side content of all time.