The default compression algorithm used is 'Deflate' because you get it for free without any external dependencies. But it is not the best algorithm for the job. It is slow. And before .NET 4.5 it also had poor compression ratio.
But even in .NET 4.5 it is still slow.
What you need to kind of asymmetric algorithm, slow on compression (you don't care, you do this once on release) and very fast on decompression (it will be used many times, every time application is executed).
I know two of them: Doboz