Combination of both. First day collections show much the audiences want to see a particular star, after the first weekend also stardom stays in contention.
Just imagine if Pk or dangal or BB starred irffan khan, kitne log dekhne aate 3rd and 4th week mein? Content needs stardom, or else manoj vaajpayee and rajkummar rao would be superstars.
Coming to bb2, its a phenemenon like none other, cliffhanger ending in the 1st part has played a big big role, imo, this is one off....even 2.0 would not match this.