For me its world of warcraft i have so much good memories of raiding with my guild.
Life is another of my favourite games along with the Neptunia series.
Gotta give it to Pokemon (Pokemon Silver specifically). I've logged tons of hours playing those games and can't wait to see what Sun and Moon bring to the franchise!
i could say the original pokemon and zelda games for the GBC, but Fzero X for the N64 has a special place on my heart, my first console and my first game, and probably the guilty of my actual music tastes XD