True, stars come and go. It is quite a revelation to watch the yesteryear stars are completely ignored by the janta and media. It shows how momentary these stardoms are. Male stars have much longer shelf life than the female ones(who last for about 5 yrs avg. The exceptional ones may reign for a decade).
However, the stature of stardom itself has come down a lot these days compared to the earlier eras. I dont think SRK, or Amir or Sallu or anyone of the present stars of bollywood has enjoyed the frenzy and mass adulation that was enjoyed by the Superstars of previous era. TV, net, media,...etc has allowed the masses many more avenues of entertainment. It has also demystified these filmi personalities. There weaknesses and vulnerabilities are much more in the open. But the same explosion of TV and 24hr media has also allowed the bollywood(and other woods) to survive(and even make profits) despite making terrible movies. Stardom is instantly gained and instantly lost overnight based on the fate of one movie. So, stardom in essence has become flavour of the season. This trend in much more pronounced in the newer generation of heroes. Also, there is no infusion of new blood. It is all a one big family business. Sons and daughters(and nephews and neices) of stars make their debuts and keep making movies in the hope that some day they will be a hit. Of course, no new face is allowed to enter. So, its a monopoly and audience have little choice. The position of directors and story-writers is a little better.
Coming to SRK, one thing about him is that he is not related to any bollywood star. So, he made it on his own in the big bad bollywood. But of course, there are 'rumours' that he had the 'blessing's of 'Bhai'. Anyway, he was never in league with the super-stars of yesteryears in terms of stature(or even movie hits). He bursted on to the scene with unconventional role in Baazigar. But his greatest hits(that are worthy of a Superstar) were DDLJ, Dil to Pagal Hai and Kuch Kuch Hota Hai. These were also the days when he truly had fans going crazy for him, specially the female species. However, even during these times he made many flops. A cursory glance at his filmography is quite a revelation.
Later, he used his past laurels to propel himself to Superstardom. His media management that involved lots of self-eulogy('Badshah') had created a perception of a Superstar, even though many of his movies did not perform as well as a Superstar's movies are expected to. Not only the box-office performance but the quality also seriously sucked. He managed to deliver some hits in between (like Kal Ho Na Ho) and many avg movies(which were 'hits' due to star power). This kept him on the throne. Partly, the reason was that he had no threatening competitor.
The problem for him in recent times has been that he is not getting any hit for a long time. All he needs is one hit(even an above avg movie), so that he and his fans can reclaim the throne by some deft media management. It is all perception anyway...
Just look at Salman who has delivered one real hit: Dabbang (which was quite an ordinary movie) and he is already being called the superstar! As I said, the stardom has become instant. Anyway, Salman was always the darling of masses(specially the muslim male audience). Ashdoc said that he like Salman for being 'secular' as opposed to the 'communal' SRK. Interestingly, the muslim male audience finds Salman more islamic than SRK. Also, the macho image of Sallu helps win their hearts.
However, I wouldnt place too many hopes on Salman being the 'next' superstar. Recall Akshay. He became the star with 'Singh is King' but quickly fell by the side.
To me, the only true star of the present lot is Amir. His movies have quality and novelty. The box-office performance has also been impressive of late.
As for the islamic-ness of the bollywood: I think bollywood has always had a lucknawi nawabi influence. The dialogue writers have penned urdu dialogues even when the characters were orthodox hindu. Infact, bollywood can take credit for popularising the urduised version of hindi. Many of the stars, directors, producers, story-writers, dialogue writers...etc have been muslims. What I mean to say is that the percentage of muslims in bollywood is much more than percentage of muslims in India. The their proportionate influence on bollywood outweighs their demographic presence in society. Of late, this is true of punjabi culture and punjabis as well. The particular influences can be better noticed in music.
Interestingly, it has given rise to a new phenomenon. The dipping image of muslims around the world has given rise to a reaction in bollywood. They have tried to restore the image of muslims through their movies. Some examples from the top of my head: Rockstar, My Name is Khan, New York, Tees Maar Khan, ...etc. The music has also become more and more islamised. Even kawwali is being repackaged and presented. Singers from Pakistan are being imported. Lyrics are laced heavily with urdu(almost persian) words.
The alternate trend has been to ape the hollywood blindly. Copying the content and style, without any attempt to make suitable changes for the indian audience. One example would be: We are family.
Anyway, I think bollywood has been in a long deterioration for a long time. It seems to have accelerated in the recent past. To be fair to bollywood, other film industries are not in any better position either.
I think the solution for bollywood lies in fresh talent(and I dont mean sons and daughters of bollywood personalities). And the movies motivated from local Indian culture, tradition, values and religion.