I still remember the first time a character's feet lined up when they walked up stairs. Couldn't believe it lol. I wish I could remember what game it was but it was SO long ago. I do remember later being similarly impressed by MGS2 stairs
The weather effects and condensation on Samus's visor in Metroid Prime had this same feeling. It's been quite a while since such minor graphical details in a game held me in such awe.