And no, I am not kidding or exaggerating - everything that follows is complete fact.
1. Spider-Man is Smarter Than Batman
Now, for those of you whose knowledge of both characters is completely limited to movies or shows, you can be forgiven for being surprised at this one, due to the unfair comparison between a billionaire adult and a poor 16 year old teenager. However, in the comics, Spider-Man is an adult as well - one who has definitely been able to use that great brainpower to fulfill his responsibilities. I won't bore you with the too many details, but some of Spider-Man's best intelligence feats include his undetectable stealth suit, holographic technology which can transform anything into anything else, antarctic vibranium spider-tracers which can melt any sort of metal on contact, cryo-pellets which have even frozen Captain America, fixing a Cosmic Cube (similar to The Tesseract from The Avengers movie) in an abandoned laboratory, curing a flesh eating disease in minutes, hacking Tony Stark's technology on the fly, teaching Tony Stark about the physics behind time travel and even equaling Mr. Fantastic's (the undisputed smartest man in Marvel) test scores at a young age! (There are many more as well...) While Batman is a better tactician/detective, Spider-Man is an undoubtedly smarter scientist.
Here is his most impressive discovery though - and the one that would be the most use in a fight against anyone - Parker Particles.
While demonstrating these particles to a group of high school students, jealous colleague Tiberius Stone sabotaged the machine, causing teenager Andy Maguire to be struck by them, gaining powers to become the superhero Alpha!
Alpha's powers, caused due to these Parker particles were so great that Dr. Reed Richards (the smartest man in Marvel) had this to say:
(For those who don't know, Sentry is Marvel's Superman, and the Phoenix is a force of the universe that makes Galactus, the eater of worlds, wet his pants)
Basically, if Spider-Man really wanted to, he could harness his Parker Particles and become a god. What could Batman do then?
2. Spider-Man Has Beaten People 100x Tougher Than Batman
For those who don't know, the aforementioned Firelord was a herald of Galactus (the planet eating guy mentioned earlier) who is approximately as powerful as the Silver Surfer. The black suit Spider-Man was wearing at the time is NOT the symbiote (merely a cloth replica) and did not grant him any enhancements. Other formidable opponents that he has beaten include Iron Man, Juggernaut, the X-Men and Phoenix Force Colossus and Magik. Meanwhile, Batman can't even beat a psychopathic clown...
3. Spider-Man Has Nearly Unlimited Resources
Peter Parker, CEO of world-leading company Parker Industries is one of the richest men in the world, and makes technology for SHIELD, as well as being a member of the Avengers.
While Batman may be richer, any difference is debatable and wouldn't make a difference anyway, when Parker's connections to SHIELD are factored in as well.
With this kind of resources, Spider-Man can churn out inconceivably advanced technology on a whim!
4. Spider-Man's Physical Attributes Outclass Batman's
While movies often downplay Spider-Man's physical attributes, Spider-Man has nearly incalculable physical strength (lifted buildings, landed planes, etc.), along with reflexes 40 times faster than those of a human. When combined with his amazing agility, durability (able to withstand hits from the Hulk or Thor) and personalized martial arts form, the Way of the Spider (created with help from Shang-Chi, Master of Kung Fu), he is a nearly unstoppable melee fighter. He should be able to take Batman down in just a couple of hits!
5. Spider-Man Has Spider Senses
Finally, we have Spider-Man's trump card - that is, Batman simply cannot hit him. Due to his Spider Sense, Spider-Man can predict attacks before they are thrown - this ability, when combined with his enhanced reflexes and martial arts mastery, renders him nearly untouchable by those without enhanced speed. A normal human like Batman, just wouldn't stand a chance!
Obviously, due to all my previously mentioned reasons, Batman has no chance to beat Spider-Man. Not only is his technology outmatched, but his skills are nearly negated by Spider-Man's own, and Spider-Man's physical attributes render Batman's useless. So, looks like poor Batman is going to lose this one... BADLY.