Here we go again :p
To me "underground" is where it is at, I was bottle fed on that music and I it's in my veins, so to speak. There is no denying about the party music vibe beeing a important part of hip hop's roots. But what you hear on the radio today has nothing to do with that. First of I will lent some words from KRS One's verse on the song Classic:
How many y’all got criminal minded you you you y’all don’t be blinded
Me I got no jewels on my neck, why – I don’t need ‘em I got your respect
KRS 1 20 years I rock I do it for JMJ and Scott LaRock – this hip hop
And we’s a nation, don’t you want to hear more KRS on your radio station?
Instead of broadcasting how we smokin’ trees, on the radio we need to hear more local MC’s
Where you at? Come on where you at? This is the difference between MC’ing and rap
Rappers spit rhymes that are mostly illegal, MC’s spit rhymes to uplift they people
Peace, love, unity, and Havin’ fun, these are the lyrics of KRS One
Now that pretty much sums it up. The party vibe thing was just that, having fun and partying, not dealing dope and blasting guns.
As we dwell deeper into this subject I feel compelled to also educate people on some things about "dance" music. Did you ever wonder why it's almost always over 120BPM? Yes there is a reason for that, I suggest you look into it and learn something new today. And that is exactly what is on the radio today, it is dance music, it is made to shake your booty to in the club. And the "mainstream" hip hop of today is starting to sound more and more like the regular club pop out there. Go to youtube and spend a half an hour watching vids on 90's euro dance tunes, then look up todays hottest club tracks... oooOO, no? nunanunaneee...
So to sum up my ramblings, the issue most of us have with this is the fact it doesn't sound like hip hop anymore. You could take out Lil' Jon and put Britney on the track and it would be the same. And that's fine, it is made to sell and to be danced to, but for us who are a tad older it feels like a robbery. Hip Hop started getting interesting and sold more and more, but it didn't sell enough so they changed it untill most anyone would accept it. Basicly they are selling a lollipop in a cigar wrapping

(and by they I'm not referring to anyone in particular.) Today nobody even blinks an eye when a hip hop track comes on at a club. Rewind 10-15 years and the dancefloor would have been empty. Dance tracks are fine, and you can't really compare it with the boom bap, apples and oranges.
Underground hip hop is made to be enjoyed, like a fine wine. It has subtle flavors that would be lost in a club atmosphere and frankly it does not belong in there either. C'mon, not many of you will go out and dance in jazz club either you go there to enjoy the music. Dance tracks are about getting your heart rate up and you moving, Underground hip hop is about expresion and skill.