(Battle City, released in 1985)
This was one of the games I remember playing to death as a child. It was brilliant, getting power ups changed the look of your tank, you could shoot through walls and it supported two players which was a big thing since my grandfather and I could play together.
(Excite Bike, released in 1984)
(included for my own nostalgic purpose)
Developing a game back then would be a hard job but if I had the funding and skill I would make a 2d side-scrolling game like the first Castlevania. I've always loved 2d side-scrolling games and if I had the means I would make one right now!