You guys that say that AIWFCIY isn't Mariah's signature song because "people don't think it's her song" are confused. It doesn't matter if people think it's a cover or not, Mariah's AIWFCIY is the one that radio plays each year and that charts worldwide every season, as well as being the most downloaded Christmas song of all time. Clearly people associate it with Mariah. Whitney's IWALY actually is a cover, but it's clearly Whitney's signature song regardless - Whitney's version will always be the definitive version no matter what. Same with AIWFCIY.