Beat Portal 2.
Overall, I'd say the entire package is fantastic but I have one grievance and that is pacing and length. Portal 1 had great pacing because it was novel and an experimental game thrown in as a bundle in the Orange Box. It was three hours long and was far too short for the formula to tire out and get boring. As a result, I have played through Portal at least 5-7 different times, on varying modes and difficulties. So I'm used to that.
And that's probably why I felt bored with half of Portal 2. As someone who really didn't pay any attention to Portal 2 news or hype, I only bought this game because it had the name "Portal 2" on the box. So I went in knowing absolutely nothing. My expectations of the game was a game without tests, Half Life with portals, basically. And the game delivered on that front in some ways.
I felt that every time I was in a test chamber I groaned because it felt been here, done that, especially given how many times I have played Portal 1. But any time the game stepped outside of its comfort zone and gave you non-linear puzzles in a more open environment, portal jumping and platforming through decaying lab walls rather than a closed in portal test chamber, the game's potential was fully realized for me.
The game would flip between test chamber and open area over and over, and I'd find my enjoyment of the game swing back and forth. Portal 1's benefit was that it was far too short to get boring, but Portal felt like a solid 12 hours with the test chamber grown tired by the sheer number of times I've completed Portal 1's various modes.
The game is fantastic, one of the best games I've played. The funny thing is that every single test, every single chamber is tip top shape, wonderful game design and yet I still found myself bored with those areas due to the similar environments.
I find that I prefer Valve's shorter offerings (HL2 ep 1, ep 2, Portal 1, HL1) far more than their more lengthy games (HL2, Portal 2). For some reason, their games shine best when you can beat the games in like 5 hours to me.
Still, the writing, the comedy, the sheer wit, and game design are unparalleled. Valve hits another home run out the park and comes away with a (near) perfect game.
Finally, that finale was fantastic.