It's hard for me to remember exactly how I felt at that young age, but I believe FF7 left the biggest impression on me as a kid. Super Mario 64 and I have always had a weird relationship where I find the game somewhat fun, but always fight with the controls, and I think that kept the game from ever blowing my mind. OOT was definitely the N64 game that captivated me the most initially (I think MM captivated me even more so later on).
Then comes Final Fantasy 7, though. I had no clue what to expect with the game, just that it a cool boxart. It was probably the first time I played something that didn't feel like a Nintendo product, I guess. I felt like I was truly on an adventure across an entire world; it was badass. I had a whole cast of characters to play with, there was this HUGE interactive story to unfold, and then you have the cutscenes? Bruh, the whole experience and existence of this game BLEW my mind.