Because she's been very successful in r&b and other genres like Pop, urban, etc something like other r&b girls haven't done yet. May I say that she's the whole package.
They aren't jealous of Beyonce's success at all. They're envious of it. They simply want something they can't have, that they may or may not feel deprived or cheated out of. I doubt they hate, are jealous of, or ill-wishing of Beyonce the person, if anything they want to be her.
Keri has been a salty bitch for absolutely no reason towards not only Beyonce, but Ciara too. What a coincidence that they are both women who have accomplished much more than she ever did (or will). No one told her to go and make a diss record about "adversity". She brought this upon herself and I refuse to feel sorry for her. I honestly think she is jealous but who knows? Maybe she was just born with a stank attitude. Her music is cute though so I'll give her that.
As for everyone else, for the most part they have shown respect towards Beyonce and that is all that matters. No one has to like her, but they can at least respect her hustle, talent, and work ethic. So I don't think that they are jealous, per say, but maybe envious of her success. And honestly, who wouldn't be? That's not necessarily a bad thing.
There's only room for one female in the R&B game at a time, you must like one, you can't like the others and since Rihanna is white...we have Beyonce and the rest of the baby mamas have to wait on that welfare line for success.
Maybe it's me but I don't see the hate/jealousy from other r&b girls, besides keri , everyone else seems to love Bey or respect her and have good things to say about her