Some men are born great, some achieve greatness, and some have greatness thrust upon 'em. Shakespeare, Twelth Night, II:5. The same is pretty much true of Super-Heroes.
Example: Thrust upon them. Spider-Man. A character given a chance in the throw-away final issue of Amazing Fantasy. Marvel was looking for something to match Fantastic Four. Spider-Man wasn't expected to make the grade, but they gave him a chance... and the readers chose him.
Example: Achieve it. Dead-Pool. A couple of appearances in X-Force, then a mini-series, and another, finally a shot at his own title. That's the hard way. Moon Knight would be another in this category - guest appearances for ages, then a shot at the big time. Cable. I'm sure you can think of many others.
Example: Born to it. Slingers, which was what made me think about about the who issue. Slingers is a carefully pre-meditated, planned, out-of-the-box super-hero group, complete with histories, motivations, fears, and a carefully structured mix of personas with neatly planned interpersonal conflicts. Not to mention the multiple variants and the Wizard tie-in, which obviously took a little bit of organising also.
There's something unnerving about this sort of planned, corporatised super-hero genesis which makes me feel less of a comics apprecionado, and more of a targeted market segment. It's the difference between farming sheep, and hunting wild-boar with a knife. Sure, in the end you get to roast something - but there's a certain spontenaity which is lacking. Hence my cautious three webs for Slingers #1 last month. If it's good, then I can forgive it it's origins. If it fails to fly, then I can say my instincts were right all along. That's the joy of fence-sitting!