Absolutely. The first example that pops into mind is Super Puzzle Fighter 2 Turbo. It was on one of those PSX demo discs and I had never come across it before that. The demo had only 2 characters and, upon completion of a single match that lasted maybe a minute, it made you exit the demo and go all the way back to the main menu screen just to play again. Even with those limitations, I still played the demo religiously pretty much to the exclusion of everything else on the disc until I was able to get a full copy of the game for myself.