On second thought -- after all, with any battle such as this, one must ask the question, Which one? Alan Scott? Hal Jordan? John Stewart? Guy Gardner? Kyle Rayner? etc. and so forth. But in this case, it's irrelevant: Any of them, even the dumbest one*, could beat Spider-Man.
*I'm not specifying which one is the dumbest one, mind you.
To me, there's no question that anyone with the magic ring should be able to beat Spider-Man. Certainly the raw power exists.
However, I don't think it's as cut and dry as everyone thinks. Number one, Green Lanterns generally aren't the sharpest knives in the drawer--brave, fearless, tenacious, no question, but we aren't talking rocket scientists. Additionally, every Lantern I can think of will happily engage in fisticuffs rather than doing everything from orbit, which would be the safest and sanest way to do battle.
Now, you have Spider-Man, who is one of the smartest men in the world, an experienced combatant who's beaten opponents in the past who've outclassed him in raw power. I would certainly give him a fighting chance.
I still think a Green Lantern should win, but I don't think that Spider-Man has zero chance.
Bwah-ha-ha! Yeah, I'll testify that I was getting really annoyed in the '70s when GL was a JLA regular but never made it past page two without something hitting him in the head. It made me think of Jim West of Wild, Wild West, who got clubbed over the head with a gun butt in virtually every episode. At first I wondered why they didn't just shoot him (that is the most obvious use of a gun, after all), but then I began to wonder why he didn't have permanent brain damage from all those concussions.
Then I remembered the battery commercials the actor did years later, and I figured the brain damage had finally caught up to him. Ditto with Hal Jordan, when he became Parallax. It wasn't the yellow impurity that drove him round the bend, it was all those times getting clubbed over the head.
I can imagine Spider-Man being able to outwit Jordan; he'd avoid those big boxing gloves easier than Octopus' arms.
Against Guy, who would probably go berserk over Spidey's taunts, Spidey would have even better odds, provided he survived Gardner's rage. But Spider-Man could definitely pull it off, because Gardner wouldn't handle the banter so well.
Kyle Rayner, a cartoonist, would actually be the one to try a huge can of bug-spray, and that would probably be harder for Spidey to dodge.
Against Kilowog, Spidey would be absolutely screwed.