I'll do the first half now and the more recent ones later:

NES: Ninja Gaiden II: The cutscenes in that game were mostly stills (with some sliding to make them more dynamic) but when you're used to your character being only a handful of pixels, these big full screen renditions were breathtaking!

SNES: Star Fox and Donkey Kong Country: Both these games pushed the SNES to its limits, the first one with it's 3D graphics powered by the Super FX chip and the other one with "Advance Computer Modeling" which produced some stunning models for DK.

N64: Super Mario 64, "It's a me, Mario" and boom that giant face you could toy with! Mindblown!
PS1: Final Fantasy VII. Those CG cutscenes and yes there was a time that even the in-game graphics were impressive.

PC (1990-2007): G-Police (fly crazy vehicles, blow things up, ROCKETS!!!), Wipeout: 2097 (see G-Police add insane speeds), Half-life 2 (long draw distance, human looking faces, Dog, the exploding building in the trailer loiked just as good in the game), Crysis (visuals were amazing)

NES: Duck Hunt (I still don't know exactly how that gun works.)

SNES: James Pond (very unique), Top Gear 2 (3D racing [Not really]!), Donkey Kong Country

N64: SM64 (Mario in 3D nuff said)

GB: The device itself was amazing to me and it was the first mobile game system I touched. After playing many games I realised Kirby's Dream Land impressed me most

PS1: This device was amazing too it had a secret function (if you didn't read the manual) allows it to play CDs. Spyro The Dragon Franchise (those portals were amazing, fully voiced cast, "Skillpoints"), S.C.A.R.S. (I only played a demo of that game, but the way the tracks were generated rightvin front of you on screen impressed me and I've yet to see anything else like it)

PS2: Another really impressive system, them 3D animated save icons. What ever happened to those? Ratchet & Clank Franchise and the Jak and Daxter Franchise (epic scope, long draw distance, massive repeatability, both games had some form of crossover, lots of animations, great stories, 60FPS), Gran Turismo 3 and 4 (broadcast quality visuals, 60FPS) Ace Combat 04, 5, 6 and Zero (crazy weapons, huge scope, dog fighting, almost photo real locations, 60FPS) some helicopter flight sim I can't remember the name of, used to fire missles just to watch them run out of gas the chase cam - activated by holding the missle fire button - followed the missles all the way to the ground where they of corse blew up in fantastic fasion.

PSP: Wipeout: Pure (bafflingly fast, really challenging, great sound design something I haven't noticed in many games before it), Resistance: Retribution (the story was good the gameplay was pretty good with nice replayability but the visuals and PS3 connection are what changed the game also the online multiplayer was fantastic - until the hackers messed it all up)

PS3: MotorStorm (Destruction!) Resistance Franchise (crazy weapons, lots of collectibles with hand drawn details, huge draw distances lots of details in environments, glitches that actually made me appreciate the scope of the levels even more!) Uncharted Franchise (amazing vusuals that improved drastically by the second game, great stories, solid gameplay, replayability, online in the last two versions)

PS Vita: when it launched it was the most powerful handheld device. Wipeout 2048 (PS3 quality visuals, CrossPlay, CrossBuy, fantastic multiplayer, incredible sound design, endlessly replayable, incredible tracks especially Sol and Empire Climb)

PS4: DriveClub (fun rewarding objective based singleplayer and multiplayer that rewards you even more the higher you place in any given race, not your average arcade racer - physics that actually require a basic knowledge of driving; The most realistic looking game I have ever seen on any platform including PC!)

Even as an idort, God of War 3's sense of scale still impresses me.

Haha! That is definitely "Wow!"! Let's try to keep the thread clean here ; ) Just kidding. This game was really hard! And quite a unique title too.

God of War 3
Killzone 2
Red Dead Redemption
Assassins Creed 2
The Last of us.

Handhelds are cool too. I just didn't note any because I couldn't think of any games that really impressed me at the time. Maybe Pokemon Red would fit in there for me.

Are you kidding me?? Silent Hill 2 in general was just pure excellence~ It definitely frightened me the most, if not "Wowed!"

Was there really nothing that really impressed you in the 7th generation? There were quite a number of excellent games there. Anything come close?

PS1: Hogs of War, Crash Bandicoot 3, Crash Team Racing, Crash Bash, Rayman 2: The Great Escape
PS2: GTA San Andreas, Tekken 5, Ratchet & Clank 3
PS3: Dark Souls, Dark Souls 2, GTA V, Tekken Tag Tournament 2, Uncharted 3, Skyrim
PSP: GTA Vice City Stories, Monster Hunter: Freedom Unite, Tekken 5: Dark Resurrection
Vita: Tearaway, Soul Sacrifice, Killzone Mercenary
PC: Gothic 2, Gothic 1, Minecraft

Haha, I don't know if I would say never. Sunshine and Galaxy were also excellent games IMO. One thing for sure is that this game set the standard for 3D games to follow.