You have familiar brands such as Yamaha, Honda, Kawasaki, Harley-Davidson, and Suzuki that can probably provide whatever you think you want. Fuel efficiency, power, speed, comfort ability, compatibility, and a trusted brand is what most people look for when purchasing a motorcycle. You will see the term "cc" (cubic centimeters) plastered on the tank or frame of every bike out there, along with a number: 250 cc, 500 cc, or 750 cc. It won't take long to make the connection that a bike that has more cubic centimeters has a bigger engine, which will produce more power and will go faster.
Some people say the bigger the better and that's when you normally see the Hayabusas, Boulevards, and ZX-14's. Majority of the time, these are the bikes you see doing the burnouts and wheelie with the option of a possible fat boy tire in the back. These are all nice bikes but its what it does for you that will make the difference. The ride you take and the comfort you get comes from the expectations you personally want to achieve.
Now those bikes may not be the bike of choice for you, but a bike with less "cc" with the same affects may be in the horizon for you. There are the GSXR's, Kawasaki Ninjas, Honda Shadows, and so on. These are more fuel efficient because they are smaller and don't require as much power. You can achieve the same thrill on the smaller bike as you can the bigger bike. Some may even dare to say that you have more control on these bikes which brings out a better comfort zone. All these bikes can be customized or accessorized to your liking and riding style.
Again, the ride you take and the comfort you get comes from the expectations you personally want to achieve. So, at the end of the day when everyone is out looking good while riding down the street on two's, stop and ask yourself... Does the size of the bike really matter?