Half-Life 2 didn't revolutionize or innovate anything. It wasn't a bad game, but I prefer the original far more, it was more fun to play. It had the standard arsenal, pistol, machinegun, shotgun, rocket launcher, with some more alien weapons like the pulse rifle. Doom did the exact same thing in 1993. The original Half-Life was impressive at the time due to the scripted sequences, but Half-Life 2 just continued something the original game did 6 years prior. The vehicle sections weren't impressive since Halo did them in 2001, and GoldenEye did them in 1997 with the tank. The physics were neat, but they had been done before but without quite as much emphasis. The original Half-Life, especially at the time had amazing enemy AI. The H-Grunts would actually use cover, dodge, retreat if wounded, throw grenades, flank the player, and used a pretty advanced way-point system to do so. Playing around with the Hammer Editor is interesting and it gives a person appreciation of how the game was set up. With Half-Life 2 it almost felt like they went backwards, the enemies all seem scripted, they'll rush the same areas, they'll use cover to a small degree but they generally just rush the player. It seems like they're on a set path as opposed to the original where they had several waypoints they could go to depending on the players position and their current health. The problem with Half-Life 2 was that it never wowed me. It was just a mediocre experience the entire time, especially with the extended vehicle sections and the platforming above ant-lion nests, it never picked up. All in all, Half-Life 2 was enjoyable enough, but completely average and pales in comparison to the first game. And it didn't revolutionize or change anything.