I know it's an old post, but I just thought I'll post this in case anyone else has problems with blurry sprites.
I've just spent the whole day trying to figure out why all my sprites were blurry with 'linear' sampling on my PC but not on my mobile (changing the sampling in project properties to 'point' did help, but I didn't like it as the graphics weren't as smooth).
As it turns out, it wasn't a problem with Construct 2 but with my graphics card settings - you need to increase the graphics quality in your graphic card settings. Now, everything should look good!
I hope this helps someone.