Well two aspects of these two characters (though not exclusive to either and not necessarily the main draw to either character) is wish fulfillment/fantasy projection in Superman and being the best and most powerful and righteously good, ethically and morally etc and then the realism, and grounded, hardworking nature of Batman. Almost unappreciated as well (relatively)  
 
So if Spider-man is about being relative, by his grounded nature and thus realistic, but also somewhat of a power fantasy/wish fulfillment, in that he may be under appreciated but hard working responsible, with powers, and also friends, girlfriends and powers (super strength, agility, the ability to sort of fly though buildings with webbings) I guess he sort of is a combination. That being said, in broad strokes a lot of characters are combinations of others. Its all relative. 

heck no.

Spider-Man has a tragic background story that causes him to use his powers for good, and altered his goals, needs, and how he feels, completely, and is sneaky and causes criminals to be scared and fear the night just like Batman. Spider-Man also has a high moral code, is the most responsible in his universe, works at a new paper, has the same colors (red and blue), and wishes he could be a regular person just like Superman. 
 The difference is he has more problems then both Supes and Bats combined. He has money problems, girl problems, has to abandon people at the worst times, goes against enemies so much stronger than him, is called a menace and is never trusted by society, and so much more. I think he sort of is a combo of the two other heroes, but has his own flavor added to the mix!

All 3  of them have been through tragedy.

Those similarities are very superficial. Having tragedy in their backgrounds and standing up for justice are things you could say about most heroes.

There is very little that Spider-Man shares only with Batman & Superman, and he simply is not some sort of combination of the two.

 I always thought of him as a combination of the two not a prefect one but a good enough one, because like Batman he was created by a tragic death that altered his whole psyche and transformed  him into an avenger of justices, but like Superman hes a bright red and blue symbol for truth and justices balancing these amazing powers with his personal responsibilities.

Those similarities are very superficial. Having tragedy in their backgrounds and standing up for justice are things you could say about most heroes.

There is very little that Spider-Man shares only with Batman & Superman, and he simply is not some sort of combination of the two.

uh...i don't really read marvel all that much, but I can tell you Spidy is not really a combination of the characters. He has a sort of playful personality while Bats is really serious (Why?) and Sups is sort of the boyscout.
I do see a comparison could be made with Peter and Clark in that they are both news houds, just of different medias (one camera. one words).
 
Also the true combination of superman and batman is this:

No, he isn't.

sneaky and causes criminals to be scared and fear the night just like Batman

works at a new paper

He has money problems

is called a menace and is never trusted by society

Those similarities are very superficial. Having tragedy in their backgrounds and standing up for justice are things you could say about most heroes.

There is very little that Spider-Man shares only with Batman & Superman, and he simply is not some sort of combination of the two.