This is an unfair question though, because especially the '90s has multiple games that are better than the other decades' 'Games of the Generation'. 
Anyway, while I wasn't alive until the late '80s, I played enough on the 2nd and 3rd Gen consoles owned by family back in the day members to know what's up about the '70s and '80s. I am basing this on the release dates of games here in Europe, which means some early games were '90s games for us, which means that there are games from the '80s I like better than the game I will list here, but aren't there because they are not an '80s game for me.
Here it is;
1970s: #14 Gunfighter, G7000, 1979 (US: Showdown in 2100 A.D., Odyssey2, 1980)
1980s: Duck Hunt, NES, 1987
1990s: The Legend of Zelda: Ocarina of Time, N64, 1998
2000s: Star Wars: Knights of the Old Republic, PC, 2003
2010-2015: Super Mario Galaxy 2 Wii, 2010







