I love reading this forum to read the responses. I'd be curious about the answers that would be given if someone asked the "If a tree fell in the forest' question.
That said Influential is as completely irrelevant in gaming as it is in acting and music. Everyone has an opinion and each one is different.
Personally? I'd say Unreal, the first one. It was one of the first PC games I ever played and I couldn't help but to sit in awe as the world opened up around me, interesting locations and dangerous wildlife. A sense of awe and inspiration that is greatly effected by my nostalgia for the game.
Warcraft 3 Custom modes like Tower defence, DoTa, X hero siege and Naruto wars
TES:Morrowind -The first massive single player game of its size with hand crafted game environments and architecture.A tradition Bethesda still continues today
Baldur's Gate did this before Morrowind.
Good to see dune 2 was already mentioned, and like a couple of other users have voiced where the hell is doom?!
Pong - the first videogame ever made. Impossible to not include I guess.
Pong was not the first video game ever made
in fact you missed out a load of old games that pretty much established the various genres such as Adventure which obviously established the adventure game.
Well, that's the whole point of raising this as a thread. So that others can contribute others XD
Tenchu, Metal Gear Solid or Thief. All 3 came out in 1998 and pretty much started 3D stealth games. Dunno which one you'd pick. I'd probably go with Thief for the use of a light/sound meter.