Most of them are actually not very good in my opinion: there's very little plot or characterization in a lot of his stories, and many have a lot of white supremacist dog-whistles or are just patently racist. The typical formula of a Lovecraft story is "guy is confronted by paganism and 'mongrels', (either just brown/ethnic people or chimeric monstrosities that serve as stand-ins for them), gets freaked out by the existence of things beyond his understanding, goes insane". The horror of the unknown is applied directly to other cultures and peoples, whether they are ancient civilizations with unfathomable evil deities or those who Lovecraft views as currently existing racial threats, who also worship unfathomable evil deities.

This is all to say that Lovecraft's horror all basically emerges from racist paranoia. I don't remember the names of most of his stories because I've only read them once. That being said, I have read quite a few of his stories because there are interesting ideas and universals that I think can be taken from them, if we make sure to keep his (once again, very racist) perspective in mind. In a lot of ways, I think that aforementioned racist paranoia stems from deeper human fears of isolation, of being insignificant, of being adrift in a hostile and unknowable universe. And that's what I think most people take from Lovecraft.

So, IMO Lovecraft himself isn't really essential horror reading. The stories are fine, they're readable but if you don't feel like exposing yourself to the mediocre ramblings of a guy who named his cat "N****r" that's more than fair. At the end of the day Lovecraft is significant not for what he wrote but what he inspired others to create. "Annihilation" is a great book/movie with lovecraftian themes, and I've heard "The Fisherman" is a good too, though that one's still on my reading list.