Aside from early producers w/ good taste in samples (and how to use them the most effectively) like Prince Paul and The Dust Bros, I basically put Daedalus above everyone else (Madlib famously sampled him on "Accordion"). He seems to approach beatmaking from a musician's standpoint, adding live instrumentation beyond your standard little keyboard loops. I also think DJ Krush is pretty damn impressive though generally a bit too ambient for my taste. But yeah I hear folks rave about producers like Madlib and RJD2 and I don't dislike them but also don't really see what the big deal is. At least w/ someone like Kanye (who makes music I have zero interest in listening to while the type of stuff guys like Madlib and RJ do align more w/ my tastes), it's pretty clear from sampling pretty much any given track why's he's considered a gifted producer.