It varies by property-the higher up the scale, the better the breakfast-Rodeway/EconoLodges might have a box of donuts and a gallon jug of OJ on the counter
Clarions may have a full restaurant on the property(but it won't be free)
YMMV at any Quality, Comfort, or Sleep-it really depends on how much the property manager cares about his/her breakfast program. I've been to Quality Inns with a nice spread and Sleep Inns with next to nothing, and Sleep Inns are supposed to be more upscale.