There are differences. In WWI and WWII there were very large numbers of conscripts. They were fighting a war which was seen as morally right - this is pretty indisputable in the case of the Nazi's, but more problematic looking at the causes of the Great War.
Today we have professional armed forces, who choose to join and are attracted to the forces for many reasons. it can be an attractive career. My brother served for over 6 years before being medically retired, and served in Bosnia. His military service opened the doors to his current career. He knew the risks and accepted them. he wouldn't say he was a hero, he was just doing his job - but he would agree that the conscripts in the earlier wars were heroes. I haven't asked him, but I;'m sure he'd also agree that the APR wardens, the Home Guard, the coal miners and the munitions workers were also heroes in those earlire conflicts.
To a certain extent, I think the current description of heroes owes something to guilt over support for the operations in Afghanistan and the invasion of Iraq. Many who did support these actions have now changed their opinion. I think it entirely fair and logical that they now seek to ensure that everyone can see they support the men and women on the front lines, whilst not supporting the campaign itself, by calling service people 'heroes'. I understand and respect their sentiments, but I don't personally agree that it's necessary.