Filters, envelopes, make stuff move over time. What you hear is the "machine gun effect". Plus you might want to google "sampling" and "round robin" techniques.
Personally, I play the VST's in Live or Cubase and export entire sections as audio and import to Reason. Spending time sampling is a killer of time and joy (to me). If I only have Reason available I use another, similar sound, and replace it once I get the VST's back on-line.