I wish I had good answers for this.
1)I don't like the retro Bonneville, and the like because I feel like they are dummed down, much like a cruiser. I do like the Ducati Scrambler, and the sport classics before them, and well as the Honda CB1100. The speed/cornering/braking limits of a modern sport bike are all so extreme that I a mere mortal can't ever touch them in the street. Sports cars got the same way which is why Mazda sells so many Miatas, the limits are just out of reach of the normal person on the street, but you can feel that you are approaching them. I would love to have a bike that didn't require work every few weeks though.
2)Old bikes are a different story and I like them all. I don't fetishize a certain make or model like a lot of people. I typically buy Hondas because I already know the wiring diagram colors and how they typically do things. I have my CB750, which was the 2nd bike I ever owned, and I have had it since 1994. When it isn't running it is just about worthless, which keeps me from selling it, and when it is running why would I want to sell it? On my radar of bikes I would like in the near future are a Honda XL350 from the mid 70s, maybe a XL500 from the early 80s, maybe an MT250 to replace my MT125, and an Evo era motocross bike, like a Honda CR480. But if my CB750 was somehow a total loss, like off a cliff into the ocean, I'd just go out and buy a 1990s Nighthawk 750, or CB1000, or Bandit 1200, or Kawasaki Zephyr 1100.
3) Not power or speed, just about everything has enough of both of those things. I used to ride a Honda C70 Passport from Van Nuys to Hollywood for work occasionally, that was the only thing I have ridden that did not have enough, but with 4 speed transmission I bet it would have. Yes the look has something to do with it. The answer a lot of people give, and I agree, is that you can see the motor. There is a certain honesty to naked bikes. I do like to cause a sensation, and make people think WTF? Which is why I built that Japanese style bike, and why I have raced unusual stuff off road, like the CL450