Launch games:
1. Super Mario 64 (N64) - Head & shoulders above every home console 3D experience by far upon its release. The level of 3D fluidity was hard to describe to someone who hadn't seen it yet. For Nintendo to knock it out of the park at this level on the first try was simply amazing.
2. Rogue Leader (GC) - More jaw-dropping than anything on even the Xbox at the time. A perfect launch showcase for the Gamecube hardware.
3. Soul Caliber (DC) - Instantly showed off what we could expect in the next generation and a full technical leap over Gen 5. Far better than the arcade game (as it should be) due to the much appreciated extra effort put in by Namco to take advantage of the new hardware.
But the biggest leap a year or two in for me on any console has to be Metroid Prime (GC). Seriously, this game had people looking at that little cube in disbelief that it could be producing visuals at that level at 60fps. The art style is unparalleled; every room feels unique and different due to the graphical architecture, and the effects, like steam fogging up the visor or seeing Samus' reflection, just sustained the visual amazement. I remember an EGM writer exclaiming, "it's like the best title from six years in the future fell through a time warp". A perfectly apt description, I must say.