The Legend of Zelda: A Link to the Past, and Illusion of Gaia, both for SNES.
Two of my favourite games growing up, still have both complete in their boxes. Have bought and sold a lot of games over the years but these two were just something special that I could never get rid of and I still play em almost yearly.
Crash Bandicoot 2. I used to play it once a year, not so much since the remakes came out. I need to bring out the OG soon.
Every Christmas I sit down and play the same map Christmas map in Viscera Cleanup Detail.
As for playing tradition. I will always fall back on Tyrian 2000, which I have dubbed as the best use of 15 megabytes you can use. It's a top down shmup from the way back that has a lot of gameplay, plenty of awesome weapons, secrets, and a decent mobile port.
Either Minecraft or Sonic the Hedgehog 3 would take that title for me
Both of those are games I've played LOTS of when I was younger (well, I am still quite young) which provided me with lots of fun and I just kind of come back to playing them periodically.
Either because there is some cool new community project I want to try or because I just miss playing the games.
Not really childhood more like teenage but mass effect is one I regularly go back to.
Final Fantasy X is a game i always come back to. Have played it already serveral times.
That scene where Yuna performs the sending in Besaid, chef's kiss Still makes me shed a tear or so after all this time.