My two cents, and I realize how old the topic is - it's timeless.
For me, Chrono Trigger gave me the same kind of feeling as Metroid. I wanted to continue, and learn more about this world I was exploring. I didn't feel like I was reading a book, and I didn't feel like I was in front of a TV with a controller. Instead, I felt like I was entirely wrapped up in this little world, and nothing else mattered much until it was finished. I still have a feeling of wanting to know more about the physics and other laws governing that world, and I want to know more about each character. It retains its feeling of mattering for much longer than the game itself is around. Metroid was similar for me in that it caused me to want to be an anthropologist (studying now).
