Hrrrrmph. After Star Trek, William Shatner has gone on to have 2 hit TV shows (TJ Hooker and Boston Legal) and a hit record. How is that not charismatic?
He was in one of the all time classic episodes of the Twilight Zone (and another that was pretty good).
He was in the only movie (AFAIK) that was ever done in Esperanto
He's arguably the greatest actor of his generation. Of the century. Of all time!
(Well, not really. But he does have a certain appeal)
Anyway, I think Mr. Card has confused good science fiction with good television. I love Isaac Asimov, Arthur Clarke, and Larry Niven, but I don't think any of their stuff would translate into TV very well. Heck, Larry Niven is mostly just an idea guy - most his stuff is not that well written and has unlikeable characters.