IF YOU HAD to be any superhero, who would it be? I think the answer says more about a person than anything else. The real challenge of picking your superhero is not just choosing which traits you'd want, but- more subtly- seeing the downside of the traits you might not want.
Superman, for example, is a perennial favorite. But some things you might not want to know. Would you really get a lot out of x-ray vision? Wouldn't you then be compelled to scan your friends for cancer on a regular basis? You'd attract nothing but hypochondriac friends. Mothers whose children had fallen out of trees would constantly be knocking on your door, asking you to give little Martha 'just a glimpse' to save them the time and expense of an emergency room visit. If something else was wrong with little Martha which you didn't detect, you could get sued for malpractice, despite the fact that you're Superman and not a licensed medical doctor.
It helps to have superhuman skills. You wouldn't want to be, say, the Question or Batman, merely relying on a series of mechanical devices which would inevitably get stolen by Proctor & Gamble and mass marketed around the world, or at least to the US military. Having a secret identity and independent wealth is key; you need to be able to turn off your superhero identity when you want to catch a break. Mind-control offers interesting potential scenarios but again, there are some things I think you just wouldn't want to know. People would stop buying you birthday presents on the excuse that you always ruin the surprise. Eventually no one would want to hang out with you. Dating would be right out of the question.
I would choose the Flash, myself. I hate airplanes and I think it would, in fact, be very difficult to find a downside to super speed. Plus I like the little earwings on the costume. Is 'earwings' a real word?
