Were they ever that mainstream? Resident Evil was the only horror mega blockbuster in the PS1 era (I'm including the first two Dino Crisis games among them since they're basically RE spinoffs) and in retrospect I don't think it was the survival horror the average gamers liked, it was blasting monsters with guns. With the exception of Silent Hill, none of the other big survival horror games came close in terms of popularity, and even then Silent Hill was a pretty distant second.

Just to illustrate what I mean, Project Zero/Fatal Frame was considered one of the major survival horror franchises of the early to mid 2000s among RE, Silent Hill and Siren, and to date the entire series has sold 1.3 million copies. In comparison, Dino Crisis 1 sold 2.3 million copies and Dino Crisis 2 1.2 million.