If Superman doesn't exist, that would mean several OTL super villains would be butterflied away. Lex Luthor, for example, only became bad because he blieved Superman destroyed his lab on purpose when it was an accident. Hence, Luthor would likely use his intelligence for good. The Conduit will not have his plans ruined by Clark so he won't be bad either. He will be working for the CIA.
However, I think the planet would eventually have been destroyed by Doomsday so it doesn't matter.
As for superheroes, don't forget, the Phantom was the first to wear the tights & mask. Pretty fair chance Bats still happens in '39, following the Shadow & the Spider, among others, in the pulps. Reasonable chance superheroes happen anyhow, too: Martin Goodman was looking for content (Torch & Subby, for a start), & other publishers were looking for ways to keep their presses running. It likely means Cap Marv never happens, & maybe not Marvel's Wonder Man, either. (Could be they happen quite a bit later, instead: Silver Age, instead?) I suspect the patriotic heroes also happen anyhow, given the war.
The Silver Age revival was partly a reaction to Wertham's stupid charges, which helped kill off horror comics, & partly the last effort of a failing publisher, Timely, which gave Stan the leeway to create FF...
There's also the Baby Boom to consider: it'll boost demand for "kiddie books", & it only takes one smart publisher.
In short, there's a lot of momentum toward superhero books happening anyhow. Just not necessarily the same ones. Good chance there's not a million-seller til Spidey debuts. Also pretty good odds Robin never happens, with no Cap Marv selling over a million & a half copies a month