These could be games that left a lasting impression on you, games that had stellar gameplay mechanics, characters that captivated you, games that you played tons of hours on, etc.
Ha, I recently saw that Toy Story 2 was in the retro library of my PlayStation Premium subscription. Invited my brother over and we spent the next day or two running thru it. Clunky as hell these days but still weirdly endearing enough to be just as much fun as we remembered.
Yeah, just a tad bit too much for me to have a "smooth" experience. But not enough to be unenjoyable or anything. Not at all. I had a blast and I'm absolutely going to enjoy my next emulated playthrough when the inspiration strikes.