Why? The game starts with a guy committing war crimes. He questions his king, is stripped of his post, and sent off on a suicide mission. Then, when he carries out his mission, it turns out he's committed yet another atrocity. That was fucking grim for a game that came out in 1991, and strong medicine for a sheltered kid who had grown up on TV that produced "pro-social" messaging like Dungeons & Dragons and The Get-Along Gang. Here was a game that gives you a taste of the kind of bad shit that can happen when you trust authority instead of your own conscience, and that was strong medicine.
So, yeah, I think games can be effective storytelling media. Just bear in mind that FFIV didn't have full-motion video, anime cutscenes, or voice acting. Hell, the original SNES release didn't even have an accurate translation; as a pre-ESRB title it was censored to suite Nintendo of America's content policies.