Yeah it's in my top 5 games ever, I like Portal and TF but Orange Box was all Half Life 2 for me.
GTA 4 was a truly amazing game, I pick it up today and the mechanics feel as good as pretty much any game you can buy. I constantly find myself forgetting that it's already 5 years old. My only qualm was the driving mechanics were a little off. I think that will be fixed for GTA V though, that's what makes me so excited for V, it's been 5 years since they made 4, they will have come along way since then.
EDIT: I was beaten to it!
The multilayer is pretty fun, the graphics are great, and the core mechanics are solid. Single-player was a little above average but honestly, I'm rarely impressed by single-player FPS games these days, and it felt like an everyday shooter in this regard.
The Walking Dead.