Depends what commercial music your talking about. See theres usually a reason why underground cats are underground.. Its usually a defining aspect of their music or their image that means they just cant sell to larger crowds.

Take Jedi Mind Tricks for example, awesome group, love their music... But Vinnie Paz is a fat white dude and their music is horrorcore underground which means real large target audiences are just not gonna feel anything their making.

I could list a bunch of others, but you get my drift. I used to be a big time underground junky untill I actually came to the realisation that underground rap as we know it, just wont sell as many copies and now a days, I actually now enjoy my style of 90's big time commercial with underground rhyme schemes a hell of a lot more than making underground shit just for hip hop heads. Its broardened my perspective on music heaps and even though I hate a lot of groups, their is certain commercial rappers I would listen to over underground any day.