YUP, I gotta agree, that intro beat on the Chronic features one of the dopest sounding beats ever. It's a shame there ain't a full lyrical song on it.
The main funky worm synth lead doesn't sound like a sample to me, but the percussion and everything else, most likely is.
All the old school fools need to do a throwback album. If they honestly think G-Funk/Mobb Funk is dead, I say fuck it, bring it back for an album or two and see how people react to it. I guarantee there's a market for it. Most people still prefer that style, they just think it's "oldschool" because no one is doing it anymore. To me it's never oldschool, it's the way WestCoast rap should always sound IMO.