i've been riding since i was like 11 and i've ridden just about every brand and size of bike out there.
for a beginner I would recommend a Honda or a Kawasaki. Honda's are lots of fun cuz they're a great all around bike(performance, comfort, reliability).
A Kawasaki ZX-6R is a great bike too because they're not all that powerful and they're pretty forgiving.
If you buy a Honda, go with a CBR600F4 or F4i. They're a great beginner and intermediate motorcycle.
With about $5000 you can find a descent 600cc bike. Just whatever you do don't buy a Suzuki, if you're not careful you'll hurt yourself on a GSXR. Yamaha's are good too but they have a uncomfortable riding position.