Call of Cthulhu is so good and it hurts me that it isn't more popular. Very very tough to get people to learn new systems even when they're not exactly GURPS-tier insanity and arguably simpler than WGRG.
I was lucky in that in high school, all of the RPG players I knew were huge Lovecraft fans. Virtually everyone I knew had read him since they were kids, so when we found out it existed it was pretty much "Okay we're going to play this." It was probably the longest and most serious campaign (or series of campaigns since the world ended spectacularly a couple times, once directly due to the acts of the players) I've ever run.
Absolutely phenomenal game, and the system is awesome. I played almost all the other Chaosium games with the percentile system they shared, which made it really easy to treat the rules as modular and graft on rules, systems, skill trees, etc. from one game to the other to create hybrids.
Also, after running many CoC games, it becomes very apparent that CoC's reputation for slaughtering players is overstated and likely just from players who treat it like a standard dungeon crawl.
I generally played it super deadly. But after the first couple near-TPKs everyone learned to calm the fuck down and be careful. I generally allowed characters who would have been massively OP in a less murderous setting, for instance, having nearly unlimited access to firearms of every sort.
It didn't take them long to learn that while guns are an excellent problem-solver for human cultists, they don't really do dick to any major eldritch. You don't bring guns to a shoggoth fight. In fact, you generally don't fight shoggoths or anything above that level, at least not directly.
Funniest event, someone saw Cthulhu and failed his SAN check. 1d100 SAN loss. Rolled a 1. Said "I've seen dead cats scarier than that." (Had seen a cat mutilated in an unspeakably wrong way and lost 2 SAN earlier.)
ETA: and as to deadliness, while someone would die in almost every scenario, including one where the TPK was because the party opted to die to save the entire world, there were a few characters who lasted years in both game and real time.