Officially, Reed Richards and Doctor Doom have no "specialties". They're polymaths that are good at all subjects, but not as good in specialties.
I never got the impression that Barbara Gordon was the greatest computer scientist on Earth. As Oracle she was clearly very adept with information systems and communications, but the title "greatest computer scientist in the world" would seem to encompass a WHOLE lot beyond that, like building your own computer systems, programming, etc. I admit I haven't read a lot of Oracle stories, but I don't remember her ever creating or innovating, only manipulating.
Also, they stole that spaceship from NASA.
Ukrainian Red CrossHmm... I think it could be argued that Babs (at least preboot) was the world's greatest... information technologist, I guess? I mean, her first outing as Oracle had her bringing down a guy who's freaking superpower was hacking. And for that matter... I'm not sure how much innovation she's done, but I have vague and possibly wildly inaccurate memories of her bringing together and interfacing something like half a dozen alien races' advanced computer tech (New Genesis/Apokoliptian, Kryptonian, Thanagarian, Oan(?), etc.) as the League's go-to girl for any and all things computer. If that's not some kind of genius, I'm not sure what is.
DC also has Ray Palmer, the Atom- Exotic Matter Physicist as a specialty, maybe?
Ted Kord was... hmmm. Inventor/Mechanical Engineer would be the best descriptor, I think. Guy invented some pretty wild stuff, like his 'BB Gun' compressed air pistol thing, or 'the bug' antigravity airship-spaceship-submarine... thing...
And of course don't forget Brainiac 5, he of the 12th-level intellect
Spider-Man always focused on biochemistry. Hank Pym would be a mix of the shrinking thing and the robotics. I always thought Reed was more of a quantum physics/alternate dimensions guy, what with the Negative Zone and the council of Reeds.
The very best, like no one ever was. Check out my Spider-Man fanfic here! [1]Reed can be more summed up as an explorer/scientist. He's basically the equivalent of the old Archeologist Adventurer and genius explorer archetype. He goes to the Center of the Earth and finds molepeople, goes into space and finds giant purple dudes, goes into alternate universes and finds green bug-people.
If I had to venture a guess, I'd say Ray Palmer was a world-class physics (including subatomic and theoretical) expert.
- Hank Pym: In the original story, he was a chemist. I'd also suggest physics and entymology (primarily ants) and robotics (though since that whole Ultron business, well . . . )
I didn't mean that Hank lost the knowledge; I simply meant that since Ultron, his interest in robotics has probably waned.
Embroiled in slave rebellion, I escaped crucifixion simply by declaring 'I am Vito', everyone else apparently being called 'Spartacus'.

Let's face it: Most geniuses in comics could be considered all-around super-scientists. But usually, there's one or two fields that they're considered to be in the category "Best On Planet". For instance:
Granted, I'm aware that these are mostly Marvel. Any other geniuses?
Embroiled in slave rebellion, I escaped crucifixion simply by declaring 'I am Vito', everyone else apparently being called 'Spartacus'.