That was the question I asked myself back in 1978. What if DC had created Marvel's flagship characters? How would they look different? What would there backstories be? Well, as far as Spidey, the backstory info seems lost but here are my visuals. Note the nigh ubiquitous cape and utility belt for adjectiveless Spiderman.
For the FF, in case you can't read my post-adolescent printing:
They patrol for crime at night! They are...the Fantastic Four!
Captain Fantastic (Reed Richards)-a police chemist with stretching powers
The Torch (John Storm)-a high school senior who can shoot fire from his hands
Monster Man (Ben Grimm)-a test pilot who can change into the super-strong, orange-skinned Monster Man
Inviso Girl (Sue Storm)-Department store saleslady who can turn invisible