I gotta tell ya, they're not really very popular at all, but damn if those Jimmy Olsen comics aren't a hell of a lot of fun. I always look for them at conventions. They're usually cheap, not all that hard to find, and I adore them. That dude got himself into some serious shit back in the day, hah.
Hope you enjoyed these throwbacks to a more innocent era in comics. While it's not the first medium that comes to mind when one thinks of horror story telling, there has always been a big presence in the comic book world. Any horror fan who shuns comic books is seriously missing out on some of the best examples of the genre available.