Hawk52: Honorable mention to Half Life.
I don't get why this is so vaulted. I liked Half Life 1. I didn't beat it for whatever reason, but I got to end game. It was fun. Nothing new though. Even for when the game came out (I admittedly played it years later), there was nothing new to it. Everything in Half Life had been done already. It just took the concepts, refined them into good control, and added bells & whistles. Nothing wrong with it.
Half Life 2? I bought it when it was on sale super cheap on Steam, and I hated it to my core. Perhaps the game improves after a period of time, but I'm the type of gamer who was bred on Platformers, RPG's, FPS's & TBS. I want to play a game at MY pace. If I feel like being a little stealthy? I should be able to. If I want to plan out my attack? I should be able to. I want choice in how I engage my circumstances. In Half Life 2, it was clearly engineered to be "The Action Movie Game", so you're just stuck on this track that moves super fast, with no ability to plan for anything ahead of you. You have more control over how you handle things in say...Unreal Tournament then Half Life 2. A good example being a bridge I crossed early on. I made sure to check it was clear. I got half way through, and a bunch of soldiers leap over the walls of the bridge and opened fire. There's no way to plan for that, and if you're playing blind you have no idea it's coming.
I get why people liked it. "Whoa, there's a helicopter chasing me, AWESOME!" but it's not for me. There's also the fact that it really didn't offer much new. I suppose the gravity gun was new at the time, but that's about it.
Most of the games that get all the praise are ones that took concepts or functionality from other games, refined them a little, and added bells & whistles to please gamers. Kind of a sad realization, honestly.
I like Half Life 2 but mostly because it was on the orange box and it and Portal kind of got me into first person shooters. It was just what I needed; it had a story I could enjoy, some characters I liked, Ravenholm, the silly physics “puzzles” and just generally the portal gun that broke up the game play enough.
Also the origin Half-Live was fairly innovative at the time from what I remember. Something to do with how it did its story telling; all of it was in game from the same perspective rather than breaking away to do it.