Although I grew up on 4th generation consoles as a kid, the 5th generation never had much of an impact on me. Maybe I was born too late for it, but seeing games in 3D always felt completely normal to me as a kid, even if it was cool (and of course at that time I could never go back to 2D games because they were obviously worse!).
I think my first big wow moment was the leap to the PS2 on the 6th generation, and while I was initially wow'ed by the first games I played on it, the biggest "wow" moment on it was probably Shadow of the Colossus, which I played two years after getting the console. The scale was just so massive, it felt like such a huge game and like nothing I had ever played. Truly the first one that impressed me on that level.
The biggest 'wow' moment I've ever had in gaming though, I think it's in the 8th generation with No Man's Sky. Say what you will about that game (well, the vanilla version of it), but those first 2 hours truly blew me away. It was something that had never been done before, I remember dreaming of something like that in a game ever since the days of Spore back in 2008 (speaking of which, that was another underwhelming 'wow' kind of game, but not nearly as much).
7th generation, I don't know what would be my 'wow' in it. Eh, Skyrim I guess?
Edit: also shout-outs to Breath of the Wild, not my biggest 'wow' moment of the 8th generation but those physics and organic interactions blew me away and still do.