AI, vehicle implementation, guns/grenade/melee and no weapon wheel, complex story, enemy variety, gun variety, graphics/art style, regenerating health, skillful multiplayer....then moving on to Halo 2....the online ranked based matchmaking and online stat tracking that at the time had never been seen before.
Halo didn't do many things first, but the overall implementation of the above ideas was unlike anything gaming had seen before.
How much of an impact do you think Halo had on the video game world? I am not asking how much you LIKE Halo. I do not like Garth Brooks or Elvis but I can respect the influence they had on music.
Your vote: Enormous impact. The implementation of current gameplay concepts coupled with new ideas had never been seen before in gaming.