There are many ways to measure how bad a storm is. Sandy was so big because it never was very well formed and was mostly a category 1 storm. More powerful storms such as Katrina were more compact and its eye was very well formed. Another reason Sandy was so big was because there were very few major hurricanes this season, which left a lot of heat in the Atlantic Ocean to be picked up by Sandy.
You should take a look at the Accumulated Cyclone Energy (ACE) for the earth (see
http://www.wunderground.com/hurricane/accumulated_cyclone_energy.asp?basin=gl ). ACE is a measure of the accumulated energy of a storm over time, and the ACE for all hurricanes can be added together to get a total energy measure. You will see that while the global ACE peaked in the mid-90s with a spike around Katrina in 2005, it's now down to about what it was in 1980. Various regions of the planet are up or down relative to that, but the overall trend in the last decade is down.
