I'm on the complete other side of this argument. The score and voiceover make Platoon and are the parts that hold up and are still relevant (This nation is still at war with itself, and the Barnes and Elias characters are just as relevant today as ever). The war scenes are bad and don't hold up at all.
Blackhawk Down was a fantastic war movie that I thought did an admirable job illustrating the chain-of-command inefficiency that was noted in the book as being a significant factor in the events, along with actual heroic actions by some MOH recipients and general badasses that made a difference. Also, I thought it did a better job re-creating Special Forces missions than any other movie before it. The weakest parts that are grating/don't hold up are Josh Hartnett, Jason Isaacs, the contrived comedic relief with McGregor and Hardy, etc., which are a small part of the film, but they do date it somewhat. If the script would have gone totally hardcore war movie without the few comedic relief scenes/lines and trimmed down the Josh Hartnett storyline, it would feel less dated, but it would have probably been a little more dark/depressing/realistic that what was considered optimal for commercial viability at the time.