I would agree with the unless you are going to do almost exclusive touring/long distances to stay away from the big tourers. I also agree with the 600 cc mark is probably about right for a newish rider.
So the 1st thing you need to do is decide on the style of bike, faired, half-faired or naked. For touring/distance riding I would suggest either a faired or half-faired bike. Will you be buying new, or 2nd hand, your budget, if you need pillion provision, even your inside leg measurement.
Then it comes down to what basically rings your bell, sports, sports-tourer, dual-purpose, roadster or Tourer. Try them all on for size etc, generally most healthy people find that a riding position that is upright/slightly leant forward is most comfortable.
Sports bike, maybe an older CBR600, very comfortable, reliable, and cheap to buy/run or maybe a GSXR750, usually same insurance as the 600 but lots of torque in comparison and also comfortable.
Sports Tourer, the CBR600F, same as above, or a Yam Thundercat, or a ZZR6.
Dual purpose. Ever thought about something like a TDM, a lot of people will tell you that it is pronounced TeDiuM, but people who own them, love them, and they are extremely popular in Europe. Also check out the versys from Kawasaki. If you are buying new, then the BMW F800GS gets great write ups.
Roadster, this is probably the biggest class, there are bandits, some naked, some half-faired and even a fully faired one. They are generally very reliable, cheap to run and there are plenty around so you can find a good one.
Suzuki also do the SV650, but these are a Vtwin, so not everyone gets along with them as the engines are definately characterful.
Honda do a hornet, but the tank range is a bit small. The also do a CBF600, its a great new rider bike, and is comfortable over the distance, cheap to run. I had one as a hire bike whilst mine was repaired.
Yamaha have the fazer and FZ, the old ones I have heard good things about, the new ones not so much, but they have also brought out a new diversion, which seems to be getting good reviews.
Kawasaki have the ER6-f which is a great little bike, as long as you are not going to carry a pillion, then they can struggle. There is also a Z750 if you want to carry a pillion.
Tourer. There is really only one middleweight tourer, the thats the deauville, which paj has mentioned above.
All in all, get out there, find a local bike meet and get talking to riders, most of us can bore the socks of you about bikes, (as you can tell, some of us more than others
) read the bike press, search the internet, there are plenty of opinions out there.
above all, enjoy