Definitely something on the Wii U, probably Mario Kart 8 it looked amazing and i could feel the next gen vibe for first time since before i just had wii and ds and 3ds didnt seem a big jump in graphics from the ds to me.

I had pc before xbox 360 and ps3 so i don't remember.
Maby Neverwinter Nights.

CoD4: MW (PS3), I was amazed.

What's the exact definition of HD gaming ?

Got my first HD TV around... 2009/2010. No idea what the first game I played was but remember booting up my PS3 on it for the first time and seeing the sparkles in the background of the XMB lol.

Later learned that it wasn't even a proper 1080p screen. It was a 1366x768 panel that accepted 1080p input.

I guess it is >= 720p

Most people with pc don't remember ofcourse because those resolutions existed on pc monitors.

Only pure console gamers maby remember their first xbox 360/ps3 game.

I used to play a few MMOs for close to ~20 years now. Are they considered HD?

Probably Half-Life with my old CRT projector in 1998, 70" screen at 1024x768 on a new NVidea Riva TNT card. The projector had 600 scan lines though, so it was downsampled a bit. It was also the first game I played on my new pro-logic surround system. It was awesome. I watched the intro 3 times before even starting the game.

My first HD ready TV was in 2004 (34"), first 1080p TV in 2006 (52") and 1080p projector in 2007. That's when I started drifting away from PC gaming as consoles had caught up clarity wise while still using 1280x1024 monitor on PC. Progressive scan made the biggest difference imo. Interlaced was always messy in motion.

Yet Half-Life will always remain my first 'HD' experience, mind blowing in 1998.

Probably a game on pc.... but unsure exactly which one..... it's so long ago, and wasn't that big of a impact I guess.

I remember the first time I saw "3D".... from a Voodoo card.
My little brother got 3DFX Voodoo card, and I remember him playing this game with a little yellow submerine... and it looked glorious.
I was 100% convinced then, that 3D acceleration was going to be a big thing.

My roommate still had an old tube TV back in 2006 when Gears of War was released. The following year he did buy a 720p HDTV, one of those LCD models edge lit by fluorescent backlights. It was... okay. The colors always felt washed out compared to the old tube TVs. Maybe he just bought a not-good model or didn't calibrate it right, but it didn't feel like a huge step up at the time. Honestly, I wasn't truly wowed by anything in HD until I saw a Blu-ray disc running on a 1080p plasma screen, and I stuck with my old late 90s 19" Toshiba until I finally bought a full HD plasma screen in early 2012.