I completed the SP in 3.5 hours
How would you- what- huh?
Also: I severely disagree with the ZeroPunctuation review of Portal 2.
The first Portal game was small, short, and relatively easy to beat, yet memorable.
The second was much longer, funnier, more creative (in my opinion), with more characters and gameplay, as well as a co-op mode.
I just don't see how you can say the first one is that much better.