Skydiving in the USA has one death per 130k jumps. Since a jump from a typical 14k feet takes about 60 seconds of freefall, that means there is a death every 2,200 skydive-hours.

There were 390 motorcyclist deaths per billion vehicle miles in the USA in 2006. Assuming motorbikes average ~40mph (between city and highway), that works out a death every 64,000 motorbike-hours.

So skydiving is significantly more dangerous per unit time.