Just so I’m not repeating with previously mentioned titles, the biggest ones I remember that give me that sense of next gen would be

The Elder Scrolls IV: Oblivion
Prey (2006)
Gran Turismo 3: A-Spec

Donkey Kong, which came bundled with Colecovision.
The pitch of Colecovision was something like "arcade-quality games at home", and they really delivered that in 82, and showcased it by securing rights to Donkey Kong.

For comparison, Atari 2600 version:

Yeah games like Prime really showed off the Gamecube's technical superiority over PS2.

Best launch title is a tough call for me; Mario 64 and SMB were incredible, but then so were the likes of Super Mario World, Breath of the Wild, and Halo: Combat Evolved.

Super Mario Bros.

I mean, just compare it to Pitfall on the previous Gen Atari 2600

Metal Gear solid 2 PS2

Soul Calibur on Dreamcast blew me away back in the days. Shenmue even more.

Demon Souls Remake, ps5. Still one of the best looking ps5 games on the console.

Agreed.  I bought, owned and enjoyed my DC via launch day.  But the ps2 very quickly made the DC look antiquated and highlighted its poor design.  The ps2 was way more powerful, had dual analogs, had dual shoulder buttons and played DVDs.  

Basically anything on PS1 or N64, even the worst looking games ad long as they were 3d that's the game that looks like it jumped a generation. For me, there's another generation in VR, Idk, the lost generation or something, Generation 8.5 and the first game that blow me away was until Dawn Rush of blood.

Not console game, so not belonging to gen per se, but it is 1992 and I still play on Amiga 500 - in Europe, Mega Drive is 2 years old, SNES and Amiga 1200 just released, and none of those systems, while all being somewhat better than 5 year old hardware of Amiga (technically 7, since Amiga 500 has pretty much same hardware as first Amiga, A1000), are really having wow factor for me (technically speaking). That I bump into this:

Comanche: Maximum Overkill (1992, PC)

This (along with Ultima Underworld and Wolfenstein 3D, both from from same year) is what cemented what my next gaming system is.