FF6 is timeless. I know FF7 was a phenomenon because of the graphics and art style, and it still has plenty of charm, but FF6 has aged better.
I love how FF6 has no absolutely clear protagonist, even if events somewhat center around Terra. Locke and Celes get equal attention and they do such a great job world-building, including [spoiler[ destroying the goddamned world and actually bringing the apocalypse. The fact that wasn't something for your team to prevent, you actually don't save the world in time, and then get to explore the World of Ruin... I still get chills thinking about the first time I went through it[/spoiler].
FF7 also removed most of the meaningful differences between character abilities, until you get into upper level Limit Breaks, since every character can learn/equip every spell or ability. FF6 presented the possibility with Espers for everyone to do anything, but you had to be thoughtful as you leveled up, making for a bit more planning, along with unique character abilities like Blitz attacks.
I'm still amazed at how much character depth and development FF6 pulls off with such simple graphics.