Starcraft (RTS, online interaction with chat rooms, competitive scene, etc.)
World of Warcraft (turned MMOs into this casual shyt we see today.. dumbed down the genre after its first initial release to double its dollars to the masses and now game companies look at it as the easier content you have you can capture the casual crowd with $$

Pretty much made the MMO genre a staple in the house hold and at the same time probably killed the genre too because whenever a new MMO comes out people just compare it to whatever their favorite expansion of World of Warcraft was and dont give any game time to grow like they did with this because the genre was still fresh to most people when it came out.. Doubt we see another MMO with its success in our life time unless Blizzard releases another one)
Diablo - You kill shyt and collect loot.. games were outl ike this before, but Diablo made it popular and also online with groups

Call of Duty 4 - FPS were all over the place before this game came out.. had World War 2 type games being released it seemed like every month then you had your UT and Quake type games.. the genre was all over the place (in a better place overall) and now everything is pretty much modern warfare regardless of series or at least the style of play
Day-Z - a million open world survival games and battle royal games have took this blueprint (and made it better)
yes theirs been games before the ones listed before, but a lot of these games in these genres pretty much took the core of these games and tried to flip it into their own. Most have failed, few have succeeded. If you know these games listed above, you can pretty much explain every popular game out right now for the most part out side of single player/platform games, which seem to be in a huge decline in popularity outside of Fallout
yall listing a bunch of games from the 80s/90s that may have been popular or have cult followings but no game in 2016 plays like them anymore.. so describing gaming to someone in 2016 and using those games as examples would make no sense, because if they went to buy a game today it would be nothing like how you described it.. yall just listing your personal favorite games and completely missed the point of the thread
this might be the WOAt tech forum of all time