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.







