i think there are several reasons why robbie's ahead of bj these days:

bon jovi is sold as a boy band between pop and heavy rock although they aren't- they're dressed up as they were 20 but they are twice as old and that appearantly doesn't work! robbie is the big everything just like madonna: he can come up with new fashion, new music style, new attitudes which people accept- and that makes him a big role-model! despite that, he's not glued to a certain music style or attitudes- he can be as mean as eminem and as lovely and innocent as Britney- and with everything he does he's funny...

bj is doomed to make rock but now they're trying to get up a new image: the old and experienced rockers who have gone softer in their music and in the things they do: no drugs, not (too) much alcohol and no scandales- and the "no big scandales" thing is not what's ´"in" these days: people sell albums with scandales and stories...
apart of that they're trying desperately to get connected to the age of computer generated music: they mix up cg and real music and that doesn't fit to a band with that history- "the boss" bruce springsteen sticks to his guitar and to his harmonica and he's more successful than he's ever been- i'd also prefer bj wihtout computers, hip-hop machines and drum-comps...
robbie's a child of cg-music and nobody gives a damn if his hits are computer generated or if he needed musicians to make a certain song (rock dj- angels) he's just robbie williams: lot's of women, lot's of alcohol, superior-minded, charming, funny, mean- he's everything and people want him to be that... for sure his life is a 1000 times harder than the life of jon or richie or any bj member cause nobody takes him seriously and nobody wants him to be serious and he'll spend the next decade trying desperately to be critically acclaimed for his music and his attitudes and gain respect as a musician- he recently said in an interview:" why do all ppl think that i can't write songs?? they don't know what's happening in my house: these are my songs, my albums, my music: i write them and i'm proud of them..." but nobody will believe... not even me!