Pokemon Fire Red and the other colors, Chrono Trigger and Final Fantasy 7 are like that for me, I played them so much and find myself playing more every now and then.
Marvel vs Capcom 2. I say it still looks and plays better than any of the newer stuff out there despite it's glitches. I mean, that roster was the first of its' kind.
i played when i was a teen, and never finished shivering island
i bought at steam and i'm playing right now trying to finish what i never did when i played
Final Fantasy Sonic X 6
If by childhood you mean that I must discard high school days, then I'm torn between DBZ BT3, Star Wars III: Revenge of the Sith PS2 and Pokémon Platinum. Hell, I might even throw in Pokémon MD: Red Rescue Team