Or, to put it another way, Martin Sheen is the new Uncle Ben Parker in "Spiderlight."
The "cute" angle on this, of course, is that both Uncle Bens will now have been played by men who also played JFK. That'll be a trivia question that endures much longer than the film is likely to...
UPDATE! Deadline says they want Sally Field for Aunt May. That's... on the nose and completely uninteresting, honestly. She'll essentially be playing Forrest's Mom again.
Honestly, this is really the only bit of casting that I'm willing to call "pretty cool" on this. It's not really "good" casting, there's nothing about Sheen that screams "perfect for it" other than the fact that "With Great Power..." is going to sound really, really good in his (very, very familiar) voice in all the trailers - which, let's face it, is what they've hired him for; he'll probably also score the voiceover gig for the innevitably crappy video-game tie-in, too.
This particular turd is still scheduled to be floating in the superhero-movie punchbowl sometime in 2012.