I agree. Sadly tho, i lean towards the latter.
Idealism is important; people need somethin to strive for. Complacency leads to stagnation. Again, in reality, even tho he owned a large ranch, it's said that the Duke secretly resented horses. His name, his walk...all artificial. It was the ideal that was to be recognized/emulated.
When the line towards realism is crossed, we get things like Unforgiven - a great movie of course, but sucessfully deconstructs the image so many earlier westerns tried to instill. I still dont think the void has been officially filled.
Your example of the Punisher is a good one, too. The heroes are grittier, but injustices wrought upon them (both by evil and neglegent systems, such as Dirty Harry's battle against the incompetent police force, mucked up with red tape) still justify his actions.
In Braveheart, Wallace seems justifed the whole way through; they took his woman, homeland etc. Details such as him killin his first man barehanded at the age of 14 or keepin "souveneirs" of his victories are left out; he's portrayed as a noble savage, rather than just a psychotic with a purpose. In that regard, the idealistic hero still exists.
But as far as the manistream has been heading for the last so many years, I'm not so sure. The idealistic hero will always have a place, but the anti-hero still seems to hold the limelight.