Most people answering a question like this will just tell you what -they- like. The fact is, there is a huge variety of choices and it depends on a lot of things, not the least being how you plan to ride it. Is it for serious transportation or just recreational purposes? Do you like the cruiser style or a sportier style? Do you want road/dirt capabilities or just road? Do you plan to stick around in town or cross the wide-open spaces? Freeways or back roads?
Nearly all bikes will do all of these things, but you know how it is, every design is a compromise. You give up one thing to get another.
You can hardly go wrong with anything Japanese. All the Japanese mfgrs make a good product, very well-engineered, good value for money, fairly economical to operate. Cruisers are for laid-back, relaxed riding, often long distances. Sportbikes are for 'canyon carving', and the real top sportbikes are very single-purpose, almost like racing machines, consequently not so good to learn on or for general transportation. There is even a wide range of 'general purpose' bikes, like the Kawasaki Ninja line, various sizes, various prices.
If you want -fast-, relax. Just about any motorcycle will out-accelerate just about any car. A 500cc bike is really small-to-medium sized but you can zip in front of anyone on the freeway. The really -fast- bikes are scary-fast. Up to 160 hp. But what used to be a 'super bike' 10 years ago is just your standard bike these days.
My own bike is 100 hp, and I very seldom use more than half the throttle. Once in a while, when I'm on a big, open road with no traffic, when I'm sure God isn't watching me, I'll shift down two gears and crank it and go from 60 to 100 in about five seconds, just for the adrenaline rush. You know that scene in Star Wars where they go into hyperdrive and the stars become streaks? It's like that.
For 5 grand you ought to be able to find something pretty new and clean and dependable. Talk to your friends who have bikes. Ask them what they like about their bike and what they don't like, and what they would recommend for your purposes. Ask to sit on their bikes--you can tell a lot by sitting on a bike!
