Heh. This gives me a wry smile. I’m a kid of the 90’s whereas my brother’s a kid of the 80’s. He grew up on Moonlighting.
I remember watching Die Hard and (at the same time, I was watching re-runs of Moonlighting - I had watched as a little kid but really couldn’t remember too well) saying “I can’t believe he did Moonlighting before this!” and he replies, “What the hell are you talking about??? I couldn’t believe after Moonlighting he went and did Die Hard! It was a totally crazy!”
Bump Ed Norton. Rounders whining pathetic wimp. I couldn’t believe the transition he made for AHX.
John Travolta made the move from Vinnie Barbarino (Welcome Back, Kotter), Tony Manero (Saturday Night Fever and Staying Alive), and Danny Zuko (Grease) to Vincent Vega (Pulp Fiction), Castor Troy (Face/Off), and Terl (Battlefield Earth).
Wait, can we ignore that last one? Please??
Also, I have to admit that Keanu Reeves came a long way from Ted Logan to Neo.
Yeah, from guy who can’t act in a rubbish film to guy who can’t act… in… a … well, you be the judge - I say that rock hasn’t shifted an inch.
Would Clint Eastwood as Rowdy Yates to Clint Eastwood as the Man with No Name, Dirty Harry, Josey Wales, et al count?
How bout the kid who used to be on Head of the Class but now is on NYPD Blue?
Do you mean Rick Schroder (“Silver Spoons”) or Mark-Paul Gosselaar (“Saved By The Bell”)?
The first film that came to my mind was Dustin Hoffman’s role in Straw Dogs.
Yes, and don’t forget Kalifornia. Pitt’s frighteningly believeable as a spree killer.
Keanu Reeves is pretty damned scary as the wife-beater in The Gift.
Hey, give him some credit. Reeves reacts well, which is what makes the Matrix movies work for him. Its his acting that is a problem. 
Mike
Tom Hanks going from Bosom Buddies to Saving Private Ryan.
Kevin Costner going from The Big Chill to … well… anything with a pulse…
My vote would have to go for Will Smith.
From Fresh Prince to Men in Black to Ali…that’s quite a transition.
Also making the transition within the space of a single film: Vincent D’Onofrio in Full Metal Jacket.
Woody Harrelson went from sweet Woody on Cheers to Natural Born Killers.
My vote goes to Eric Bana. From stand up and sketch comedy characters and Con Petropoulous in “The Castle” to underworld killer Chopper Read in on smooth transition.
Tom Hanks is a close second.
No mentions of George Bush Sr. yet?
(For our younger Dopers: during the 1988 presidential campaign, the media label for Bush was that he was a wimp – one major newsweekly even famously ran a cover story entitled “The Wimp Factor.” Fast forward a few years, and Saddam Hussein invades Kuwait, the US puts together Desert Storm, and those same newsweeklies start writing about how Bush has shed his wimp image. I dunno if Bush Sr. actually is or is not a wimp, but that’s the way the media ran FWIW.)
The Matrix (the original) works because Keanu Reeves only acting talent is a ‘what the f-ck is going on here’ character (see also: Bill and Ted’s Excellent Adventure).
In Reloaded and Revolutions, he’s supposed to know (essentially) what’s going on, which he does horribly.