I bought myself a bike in April of '05. I had never riden anything over a TINY single speed 50cc dirt bike since I was around 10 or so(34 now). I did take the motorcycle rider safety program(which I HIGHLY recommend-
http://www.msf-usa.org/ )before I made my purchase. It gives you the chance to learn the very basics in a controlled slow paced environment by professionals. The best thing is that THEY provide the bikes(usually 250cc cruiser type). By taking the class, not only do you learn how to ride, but most importantly, if you will actually want to purchase a bike and ride afterwards. All to often I hear people say they want to ride(who have never before), go out and buy the latest greatest "toy" and a few days/weeks later totaly hate it and now they are stuck having to get rid of it. The course is just over $100 if memory serves me correct...try and find a decent used bike for that! It will be money well spent!
Now trying to quickly answer the starter bike question

I know I've been quite lengthy already, BUT it is your life we're talking about!!!!! The WORST thing you can do is listen to people who will tell you to go out and get the biggest motored cruiser or the best liter bike a company makes("you won't be happy with anything else after a few months or so and want to upgrade")that you can afford!!!!! You know what? Start out VERY resonable and you can always upgrade the bike, but you can NEVER get your(or anyone else's) life back!!!!! The greatest contol you have over ANY bike is your right hand. That is the only thing that dictates how how fast you go. Sure you could jump on a 'Busa or "Gixxer" 1000 and use minimal throttle and survive so you can look cool(huge waste of money though), but when stuff goes wrong and you pull just a bit too much throttle...many things go wrong REALLY REALLY quickly!!!!!!!!!!!!!! Both of those bikes stock have in the neighborhood of 170 HP. An inexperienced rider can get into trouble just as easily with well less than 100 HP! So I agree with the likes of the Ninja 500 or a 500cc cruiser as a starter bike. You can pick up great used ones for very little money, put many miles on them gaining experience all of the time, resell them for nearly what you paid(if not damaged of course) and upgrade if you want later. A bike is MUCH different than a car!!!!! Your chances of survival in a car are much greater if/when you get in over your head from time to time by exceding your limits. You need to approach it with your safety in mind at ALL times! Don't go out and try to "hang" with the better skilled riders on the open road or in the "twisties". On a bike(unless very well practiced), you get fixated on an object...you will ride right to it! So if you follow seasoned riders off into a corner at 50 MPH and the sign says 25(given good road conditions-most bikes can easily do this)...you have just exceeded your newbie skills and are now relying totaly on luck. You may know what to do in your head, but until you practice it, you won't perform it.
Sorry to really drag this out, but like I said earlier, IT IS YOUR LIFE or whomever rides with you or that is around you possibly. I wish you the very best if you decide to persue riding. It is VERY fun and rewarding at the same time. You can't get the same experience in a car even on the same exact roads at the same speeds.