Since I've heard about Aeris being killed by Sepiroth before, I went ahead and watched it on YouTube, and I wasn't impressed. It must have been because I didn't play the game. If that scene affected you at all (if it looked like anything but cheesy crap animated with expressionless plastic dolls) it was because you were prepped by playing the game to experience that scene in a particular way. You can watch a clip of "La Strada" or "Midnight Cowboy" or "Unforgiven" or "Casablanca" out of context and at least get a sense of the emotional dynamics of the characters. That's the strength of movies. The strength of games is the immersion and feeling of personal involvement with the characters, personal involvement driven by your own actions, choices, and sacrifices. I may have felt like Ratso Rizzo was my friend, but I never picked up a john to get money for a bus ticket for us to leave town together. I may have shared Rick Blaine's feelings as he put Victor and Ilsa on the plane to Lisbon, but I didn't decide to do that. It just happened to me.
Games will always be second-rate next to movies when it comes to presenting scripted drama, but they don't have to feel that way. Aeris and Sepiroth is proof of that, I guess. Gameplay allows games to affect us in ways that movies can't and enables different and stronger emotional contexts for experiencing games as art. The art of games is in the gameplay. Detaching from gameplay is just a crutch, like filming a stage production, copying another art form because we don't understand the new one well enough yet.