I have always been a Nintendo boy, and played a lot of Mario games, but I think what really was the most important would be Galaga '90 for the TG16, or Super R-Type for the SNES.
My first console was actually a TG16, only bec we couldn't find an NES at the time, and I always played Galaga '90 on it. We also had Military Madness, Neutopia, Psychosis, a few others, but the most hours went towards Galaga.
We eventually found an NES and got a bunch of games like Mario bros./duck hunt, final fantasy, laser invasion, contra, super C, and other I cant remember.