Braid's plot is shaped by Jonathan Blow's personal beliefs on narrative and its relation to game design, and it's important to understand them before simply dismissing the plot. (Incidentally, I do not agree with most of Blow's ideas.)
Saira has a simple, up-front plot that serves as framework for the gameplay, and motivation for the player (finding Bobo). Braid has multiple levels of plot- the simple, up-front plot which motivates the player to continue (finding the princess), and then other levels of plot which you can disregard entirely without sacrificing much.
Yup, I know. I actually have a copy of a very interesting talk Blow did about narrative in games. I've also read numerous analytical pieces about how the plot is supposed to work.
I just don't really think that it does work the way it should. I should also say that I don't necessarily just dismiss the plot of Braid. There are a lot of interesting things going on in it and TONS of symbolism. I think Blow is a very smart person and he has a lot of interesting things to say about games, but he suffers from the problem of knowing that he's a genius. Braid feels to me like a little kid jumping up and down going "I'm so smart!", "I'm so clever", "I'm so great". And in many ways it is all of those things. But in some ways it's also a murky mess of jumbled philosophy. I think Blow's work will improve if he just relaxes a little bit and doesn't try so hard to be what he already is.
Nifflas' games capture narrative in the gameplay so smoothly. He builds worlds that feel lived in and real. Yes, the story is very simple and serves mainly just as motivation to continue...but the real story is the story created by the worlds that you travel through and by your actions in them. His genius is the way he lets you explore these worlds and discover their secrets. You almost feel like a real participant in how the game unfolds.