Edit: Yes, I have missed a P in the title, if a mod is friendly to update it
Right...there's a theory I have here and wanted to see what other people thought.
Guns N' Roses arrived right between Slippery and New Jersey. And while many people think that Slippery actually paved the way for Appetite to become the success it became, I also think that Appetite greatly influenced New Jersey. Bon Jovi definitely went in that direction, which made New Jersey the success it became.
First and foremost, it's a much heavier record than Slippery. Be it the opening riffs of Lay Your Hands on Me, the distorted guitars on Wild is the Wind or the grit and heaviness of Homebound Train. Then, New Jersey is the first BJ record where you can hear BLUES influences. Be it I'll Be There For You, Love for Sale or again, Homebound Train which is nothing but a blues song on steroids. Appetite was basically a very heavy blues record mixed with some punk and Bon Jovi took some of that into their sound. Then, there's Jon's vocals which sound a lot rougher than on Slippery. There's moments where they are menacing even...like the "Ha!" in Lay Your Hands on Me. And maybe last is the increased "sexuality" of the lyrics.
Of course, Jersey still had the safe trademarks of Slippery, be it Born to Be My Baby or 99 in the Shade but overall, it moved closer to what Appetite represented. Jon was even wearing a MISFITS patch on his coat.
You might say it was just a natural evolution of the band, which I actually also believe. There's unbelievable songs like Living in Sin or even I'll Be There for You which would be outside the reach of Guns n' Roses. But overall, I don't think New Jersey would have quite become such a monster of a record, without the arrival of those 5 mother****ers from Los Angeles.
Edit 2: And yes, together with Back in Black, these are the two best hard rock records of the 80s, hands down!