My entries may be skewed since...
1) I'm American - Northeastern corner too so it was almost totally consoles or x86 machines up here. My first look at an atari/commodore computer was 5 years ago...
2) I've played way too many of these things...
3) I have extremely odd tastes.
So just off the top of my head, in no particular order:
1) Yoomp! (Atari 8-bit):
The reason SIO2PC was invented.
... not really but it seems it. I'm seriously considering a DualPokey mod to my 600xl just to hear the dual-channel audio!
2) Alternate Reality: The City (Atari 8-bit):
3D explorable RPG made in 1986 - deeper than possibly anyone knows and one of the first games where literally you can have your choices come back and bit you in the ass. I love this game, and yet still can't get to a tavern for one full night's sleep. This was made when I was 4?
3) Veil of Darkness (PC/DOS):
OK, so I have a thing for vampires - especially in gaming. I've read "I, Strahd" a good 6 times and played more Ravenloft campaigns than I can remember. So when I saw this game in 1994 (although it probably came out earlier) I was floored. To me I saw a dark, intense point and click much like "Indiana Jones and the Temple of Atlantis" but with vampires and horror. I still love this game - and the intro is just too badass.
4) Final Fantasy VII (PSX/PC)
Oh come on. Your jaw dropped when you played the demo too. 3D summon spells??? When I first summoned Leviathan and blasted my enemies away with a literal 3D Tidal wave... I was lost. Sure, the plot has holes you can drive an 18-wheeler through but it sure was ground breaking. I wish I had kept my 3 preorder shirts though... they seem to have the trade value of wood from the true cross now.
5) Final Fantasy III (SNES)
I cried at the opera scene. Still - I didn't think too much of this right off the bat. I kinda liked FFII... tried FFIII and was first blown away by the opening intro. It seemed to take everything good from it's prequel and add more to it.
THEN - you got Sabin in your party. Then I used a street fighter-like fireball motion to make him do an atomic suplex. I knew I was done there.
6) Culdcept (PS2... unless you can read Japanese. Then Saturn :P )
This was more the concept than the graphics. Monopoly plus Magic the Gathering. Win.
7) Mortal Kombat
I HATE this series. But when I was 12 I was still at the arcade being wowed that Sub Zero could pull the guy's spine out. That was nuts.
8) Jet Set Willy (pick one - I play the 2007 A8 Remix):
I'll admit it - I'm a masochist gamer. There aren't a lot of platformers around that stay challenging after a while. I can hit World 8 in Super Mario 3 without thinking about it. I've been able to one-life Mario 2 for a while now as well.
Jet Set Willy destroys me every game, and I love it.
I've made it past the Banyon Tree only twice in maybe 200 or so runs. I've maybe gotten 21 items in a go. I will beat this someday. Maybe.
that's it for now, I could probably go for days though.