Resident Evil, no question. I'm not a fan of all the games in the series, but I'd say 80% of them I either really enjoy or I absolutely love them.
I enjoy Silent Hill, at least the ones I've played, but to my understanding, the series is essentially the first three are great, 4 is good depending on who you ask, and then the rest range from wildly mediocre to complete trash. Giving up Silent Hill 2 would absolutely pain me though, just saying.
TLOU is an amazing game, and while it has some fairly annoying narrative issues, I am actually one of the people that liked TLOU2. However, neither the first game with how well made it is, or the best parts of Part 2 can hold a candle to RE for me.
I've never played a Luigi's Mansion game so I can't really judge them. However, I will say I'm still somewhat bitter that Luigi's Mansion was Nintendo's follow up to Super Mario 64, and not a game that felt like more of a direct sequel. I have a hard time saying Sunshine is a sequel, even though it technically is. I really don't think a proper successor happened with Super Mario 64 until Super Mario Galaxy.