If you have not ridden a motorcycle before then without a doubt, get a dirtbike first! Learning to ride in the dirt has many advantages:
Dirtbikes are ment to be dropped. EVERY new rider is going to drop their bike. Moving it around the garage or going slow around a turn, it will happen.
Dirtbikes are easy to fix. A clutch or brake lever is $5
Dirtbikes look OK if the plastic is scratched.
If you learn on the dirt, there will not be any 3000 lb cages right behind you and comming at you at a relative velocity of 150 mph! (you are going 75 and the SUV is doing 75 in the other direction)
The controls on a dirtbike are identical to a street bike.
The reflexes you build while riding dirt will help imensly on the street. The first time your rear breaks loose, you will not panic.
A dirtbike will teach you respect for the machines.
Want power? A large 2 stroke dirtbike (CR500 is my personal choice) has almost the same power to weight ratio as the Hayabusa
I have taught many children to ride and it is definately best to learn in the dirt!
Good luck!