Heidfeld's the better Renault driver this year! 
And what exactly has "Senna" proven? Forget HRT, he didn't really set the track alight in the lower formulas now did he? That name has been carrying him through, and now in F1!
On the other hand, Nico Rosberg has the name...AND the talent to deserve a top seat! No one's complaining about him filling up a seat in Mercedes!
Having nearly a decade out of racing then coming back and being competitive in the shark pool that is lower formula racing almost immediately is nothing short of incredible. That is
not an overstatement.
In the 2008 GP2 season, he finished runner up, 12 points behind Pantano who won. He was robbed by two unfair penalties in that season, and also had a dog run in front of his car in Turkey forcing him to retire. He won the feature race at Monaco.
In that season he finished
ahead (and in some cases WELL ahead) of many other drivers who have since graduated to F1:
Di Grassi
Grosjean
Petrov - yes he finished ahead of the driver he'll be joining at Renault by nearly double his points haul
Maldonado
Buemi
Chandhok
D'Ambrosio
Kobayashi - by six times his points haul
He finished ahead of all of those, some of those I'm sure you'll consider to be decent F1 racers? They're not all terrible?
I think the complete opposite, people judge Bruno much more aggresively because of his family name. Any other driver without that family name would be judged on the basis of being runner up in GP2 with a win at Monaco and beating that list of drivers as being quite formidable.
He's never going to be as good as his Uncle, but then you could count on the fingers of one hand the amount of people in the entire history of F1 that are / were...
Favourite racing series: F1, Indycar, NASCAR, GP2, F3, Formula E, Trophee Andros, DTM, WTCC, BTCC, World Endurance... etc. etc.