I don't want to go spoiling Portal here, or even talk about it at length, because after all it is a Braid thread and I just wanted to make a quick comparison, but I will just stick to what I said that that it is one of the finest ideas of interweaving narrative and gameplay together.
As for Braid, I'm not saying that it doesn't do all that, but the concious effort to put the narrative (which I thought people kept saying that it doesn't have a narrative in the traditional sense, but) into the gameplay. And all that is symbolization, to understand underlying narrative behind all it, you are forced to read all the books, which takes you out of the core gameplay. I'm not saying it is a bad game at all, or even the story is bad, I'm just saying the way that it is presented, at least in a traditional sense, is quite poor