Almost everything in the supermarket "snack isle" is bad: chips, crackers, cookies, all that crap. Just read the labels. Its all processed flour, oil, salt, sugar.
That said, you don't have to avoid that stuff entirely. Just don't eat much of that stuff. Some folks I know will sit down with a bag of chips and polish off the whole thing in like 30 minutes while watching TV. They probably ate 3000 calories of crap right there.