I'll give it a 10. I did not like the original-riff version. It seemed Mike had too many riffs about Bela Lugosi and heroin, and after awhile that felt like it was getting mean-spirited. In the 3-riffer version, when Bill Corbett says "Oh Bela, was heroin really worth this humiliation?", that sounded more like genuine sadness that Bela had fallen so low.
I liked the 3-riffer version so much that I also bought the "On Demand" version. At this point I've watched it so many times that I can't help but think of all the other riffs they could have done. It's amazing how many plot-holes there are in this movie!
I think rifftrax just work better when there are at least two riffers. That allows one to make really bad jokes (such as bad puns), and then have someone mock-hit him...
Detective (actor): "Say lieutenant"
Kevin: "Okay. . . . 'Lieutenant!' "
(heavy slap sound)
Kevin: "Ow! I'm sorry!"