I'm gonna suck FF7's dick some more because i like it.
But the way Cloud opens item chests in the game is pretty slick. Not only will he reach for the opening button with whatever hand is closer to it, but he will also reach around the chest from the back if you open the chest from the wrong side. That level of detail is crazy to me because they could have ignored all of that and nobody would have given a shit. But the fact that they literally gave Cloud a reach-around animation for chests is nuts.
That and the sheer amount of dialog given to NPC's in some areas. During the Hell House boss fight, the announcers have voice lines for every possible attack magic, every possible summon, and every possible combination of getting hit by attacks. No matter what they have a voice line for it, and that's absolutely wild considering that 99% of players will miss a lot of that dialog simply playing through the game.
During the Aps boss fight, the arena you fight him in is surrounded by sewer sludge water and if you set Aps on fire (with magic), he will jump into the water to put the fire out before jumping back into the fight. Something that does not occur if the player doesn't use fire magics during the fight.