If I'd have to keep only one videogame, it'd have to be Half-Life 2. This is the best FPS of all time.
When I first played Half-Life 2 (back in 2008), I was very impressed with the 3D graphics. The water in the game looks really great, as well as the explosions. The 3D models are greatly detailed and the textures, in high resolution. I must say that this is the game that looks the best without asking the most out of your computer.
The game's controls are very responsive and you really feel part of the action. There is no invisible walls, no glitches, no nothing. Also, the physics system is pretty good. There are lots of weapons to choose from, as a gravity gun that lets you move objects around and the classic crowbar. The level design in Half-Life 2 is top-notch, as each level has a different feel to it and they are not repetitive at all. You are never doing the same thing over and over again, and you are probably going to find some levels that you like way more than others.
In the game, you'll fight your way through City 17, fight zombies in Ravenholm as well as drive a buggy on the coast in order to stop Dr. Breen from releasing his evil plan.
The story is pretty important, and there is no cinematics were you are disconnected from the first person view. This means that you can move around the talking characters and that you are always free to move.
Another thing I especially like about Half-Life 2 is that it comes with the Source SDK (under the tools tab of steam) that lets you create your own singleplayer maps. I'm actually learning how to use it, and it's pretty awesome compared to other editors for two reasons:
- It's very intuitive and it has a great interface
-There are lots of online tutorials in order to get you started. By the way, I really appreciate it when people make tutorials. It lets lots of people the chance to learn how to make their own maps. The tutorials aren't released by Valve, but by the Valve Community(persons like you and me).
Because it lets me a chance to learn how to make maps (one of my biggest dream) as well as to enjoy an awesome campaign, I do think that Half-Life 2 deserves a 10 out of 10. It's my favorite game of all times and even with newer titles coming out, Half-Life 2 is my favorite one.
So I really recommend you getting it, or you'd be losing something really special. Anyway, I hope this wasn't too long for you to read... xD
*You should get "The Orange Box" which includes the game and four other games which are as great as Half-Life 2.