I love threads like this.
A few that come to mind for me:
Final Fantasy IV - as a kid discovering there was an entire world underground was pretty mind blowing.
Final Fantasy VII - Again, you kind of had to be there for this, but I remember when this game came out my friends and I thought this game was going to be a deviation from the typical Final Fantasy/JRPG formula and be entirely contained in Midgar. The way the game started certainly made it seem that way. Then after 7 hours or so you escape Midgar and have the entire world map presented to you. It was a "holy shit" moment if there ever was one.
Mass Effect 1 -
A few that come to mind for me:
Final Fantasy IV - as a kid discovering there was an entire world underground was pretty mind blowing.
Final Fantasy VII - Again, you kind of had to be there for this, but I remember when this game came out my friends and I thought this game was going to be a deviation from the typical Final Fantasy/JRPG formula and be entirely contained in Midgar. The way the game started certainly made it seem that way. Then after 7 hours or so you escape Midgar and have the entire world map presented to you. It was a "holy shit" moment if there ever was one.
Mass Effect 1 -
A few moments for me. Both on Virmire. I didn't do Wrex's side quest and he got shot dead by Ashley. I was not expecting that to happen to a main character. Then the Sovereign interaction in Saren's base followed up by sacrificing Kaidan/Ashley. At the time I hadn't really seen two main characters just offed like that combined with the reveal of the Reapers just took the game and series to another level for me.