Funny you brought up Doc Savage. I had an idea for a shared comic universe of old pulp heroes. If I could ever get the rights, this is what it would look like:
Doc Savage: It'd center around Savage serving the role of the old school scientist adventurer, taking risks in his persuits and also serving as something of a paranormal investigator and debunker, both confirming real strange happenings and exposing the fake stuff, getting him in all kinds of trouble. It'd be like all the best parts of Hellboy, Fantastic Four, Indiana Jones and Planetary rolled up into one badass action hero.
The Shadow: Based a bit more on the film than the old pulps. Lamont Cranson was a wealthy man who had been born with limited psychic abilities that he'd spent most of his life trying to ignore. After "the war," he drifted through southern Asia, and eventually fell in with the criminal element there, becoming a fairly violent gangster and drug runner. However, after his small criminal empire collapsed around him, he was left with nothing. Wandering aimlessly, he found his way to a Buddhist temple. There, the monks gave him shelter and helped him find the inner peace he failed to acheive with violence and vice. They also taught him how to master his psychic abilities, at least enough to influence other people and make people not notice that he's there, effectively making him invisible to all five senses (while people do see and hear him, when he's using his powers, they tune him out as if they were simply not paying atention). This power is, obviously, useless on security cameras. Anyway, he heads back to New York, where he decides to use his newfound skills and wisdom to help others. and mayber redeem himself a bit. As such, he sets himself up as a vigilante detective, helping the helpless and trying to bring down those who would prey on the weak. I'd characterize him a bit differently, I think, in that he'd be alot more zen and spiritual in his outlook, and would be far less violent. He would also, due to his powers, be drawn into investigations of the supernatural. He would encounter fellow superhumans, demonic possessions, and other forms of crazy ****e. In many ways, the series would resemble Angel, albiet with less over the top supermnatural elements and more facing of normal human corruption.
Fu Manchu: This would be a series mostly about the villain. Fu Manchu is a scientist, mystic, and wanted onternational terrorist. As leader of the Si-Fan, his terrorist organization, he seeks to bring the world back to a better way. He feels that humanity has become corrupt and bloated, slowly killing itself with trans fat, television, and apathy. He feels that governments are inefficient, and all the suffering of the world could be solved with a firm hand. He also feels that humanity has misused science, and has lost touch with anything truely spiritual or artistic. His main goals are to overthrow world governments and replace them with an "enforced monarchy," tack a step backwards with technology as a whole and start over, teaching people how to use it properly and respectfully, and bring back some culture to the world. He is opposed by Denis Smith and Dr. Petrie, two British inteligence agents charged with the task of bringing him down. One thing that would make the series interesting is that the villain of the peace, Fu Manchu, is a far more pleasent individual than the hero, Smith, as Smith is quite racist and jingoistic. Of course, Fu Manchu is a monster. But you could get along with him quite well is what I'm saying.
John Carter of Mars: A Civil War soldier who had been abducted by Martian aliens and made the hero of Mars. Basically, Adam Strange before Adam Strange. Due to his fighting prowess, and greatly enhanced strength and speed due to the lower gravity on Mars, he certainly lives up to his job. The series would start with him returning to Earth to become Mars' ambasadore.
Tarzan: Basic Tarzan stuff, I guess. Fighting African warlords and demons and the such.
The Spider: Richard Wentworth, a man born into poverty who, through his talant and determination, became quite wealthy. After his experiences in "the war," he returned to New York where he felt fairly lost. He became something of an amature detective, which grew into a fairly unhealthy obsession and eventually vigilanteism, protecting his old neighborhood and other such poor areas. As The Spider, he's incredibly violent, often killing his enemies rather brutally. This puts him at odds with the police and the much more pacifistic Shadow. His stories would be more straight crime noir.
G-8 and O-5: Now, I know that G8 and Operator No. 5 were comnpletely seperate characters from completely different companies. But both were code named high action spy guys, and other agents in Operator No. 5 had a letter-number codename like G-8. So, abreviate Operator No. 5 to O-5 and have them both be members of the same black ops unit. Jimmy Christopher, code named O-5, was as FBI agent with a pechant for recklessness and a brilliant detective mind before he was recruited for a black ops CIA programme. The enigmatic G-8 is a slightly more seasoned member of the group, a former member of 1 SOW (air force special forces). Both together and seperately, they deal with the threats to national security that the government doesn't want mentioned.
Obviously, it would grow from there. And of course there would be at least one team up of Fu Manchu and John Sunlight.