Ditko is one of those fellows who never stopped creating. Apparently he's still creating new comic characters even now, in his 80s. Jack Kirby's health finally slowed him down, but Ditko keeps finding ways to work through the physical limitations of old age to come up with original stuff.
After Ditko left Marvel he continued to come up with new, bankable characters. Almost everything he did after he left Marvel are still being utilized by the various publishers who own the rights to them. His version of the Blue Beetle was revived, as was the Creeper, the Hawk & Dove, etc.
The most personal of his creations that ended up out of his hands has to be The Question. Philosophically, the superhero character Question is very similar in many respects to the Ditko-owned character Mr. A. Unlike Mr. A, The Question was owned by Charlton Comics and fell into the hands of DC Comics. With DC, the character had a pretty long run in his own title, but I don't recall ever reading any of those. I probably cracked the covers now and again, but without Ditko at the helm, it just didn't interest me.
The Question is a classic Ditko work. The hero sees everything in black and white, good and evil, and is typically a Fascist (as most Ditko characters are). This makes for some queasy reading, but excellent storytelling.
Charlton flirted from time to time with superhero comics, but I'm not sure what their sales were like. Captain Atom had a long run and has stood the test of time. After Ditko left Marvel he worked quite a bit at Charlton trying to generate some momentum based on his then-status as a fan favorite. But, as we all know, comic book fans are notoriously fickle. That status apparently did not translate into further success at Charlton and DC, even though the characters and the stories were every bit as good as those he created and generated at Marvel.