I personally agree with Motorcyclist magazine about finding the proper new bike by looking at weight, handling and throttle response more than displacement and horsepower.
I started out on a Kawasaki ZX1000R, managed to drop it several times by stalling it and finally got rid of it after dropping the clutch at a stop sign and doing a 360 with the bike and tossing myself a good ten feet from the bike...All in the first 250 miles of owning the bike. The weight and how far out the clutch engaged were too much for a new rider, especially one weighing only 155lb.
My next bike was an SV650, which I love and am happy to say I've covered almost 1000 miles in the first month of ownership. I haven't even come close to dropping the bike and only stalled it a few times. I feel confident in town and the only time I start to wish I had my old ZX1000R ninja is when I'm traveling at 60+mph and the fairing, increased weight, and longer wheelbase would make the journey more enjoyable/relaxing.
I will admit I started off on the wrong bike entirely. I started off on a bike that was the fastest production bike in 1987 and is still right up there with newer stock 600s. 158mph is more than too much for a first or second year rider IMO. The bike also weighed too much for me to control, coming in at a massive 580+lb wet weight. The SV650 however, weighs just under 420lb with all its fluids.
I will say this though, even though I've had a great experience with the Suzuki SV650, it's a bike that needs to be respected by new riders. Even with just under 70hp and 'only' 650cc of displacement, it can spin the rear wheel in a corner, wheelie on demand and quickly hurt your body and ego in a second.
I would say that a rider with limited dirtbike/streetbike skills and can honestly say that he has self-control and is not ego driven to drive harder than he knows he can will do well with an SV650 as a first bike.
All others, be it novices or those on the weaker/lighter spectrum should consider a Suzuki GS500, Ninja 250, or Ninja 500. I put the gs500 before the ninja 250 because it has a more relaxed seating position, probably slightly slower and more forgiving steering angle, and no plastic to get damaged in the case of small speed spills.
start slow and take your time to go faster...you will ultimately be a better and more skillful rider...speed can wait...don't be a hero around your friends or girls and try to impress them by doing stupid things or buying a huge 1000cc bike...you'll only look like an idiot...