Dangerous = at higher risk...

I suspect there isn't a simple, one-size-fits-all answer as it depends on the types of roads, density and speed of the traffic, the time of day, and of course your experience and skill as a pilot on the motorized or non-motorized machine.

That said, I suspect if you checked the stats, you're probably far more likely to have an accident on a motorcycle than the bicycle. As a subset of the motor vehicle accident stats, motorcycles are probably involved in more accidents with other vehicle traffic than bicycles because they interact directly with the motoring public and compete for the same lane space. In either case, you're more likely to be seriously injured in the less frequent encounter between your bicycle or motorcycle and a car.

But, for sake of argument....

Highest risk / frequency = bicyclists and pedestrians in dense urban areas.

Highest risk / severity = motorcycles ridden on multi-lane highways or through highway intersections during rush hour.

Lowest risk / frequency = motorcycle in rural/suburban/urban areas on two lane roads in light to moderate traffic.

Lowest risk / severity = bicycle in light rural/suburban/urban areas on two lane roads in light to moderate traffic.

Oh yea, I do a short training ride on my bicycle at 4:30am before hopping on my motorcycle for my commute to work at 6:15. Rural/Sub-development areas near home and four lane city roads closer to work.