Bruno outperformed Karun and Sakon. There were rumours throughout 2010 that Hispania weren't giving Bruno the same chances, e.g. Karun's car was the first to have a segregated fuel tank, etc. Besides, a car that is so off the pace is difficult to really judge how good the drivers are. In all races he would have had to deal with blue flags, and qualifying and setting up the car is more of an excercise in keeping it on the track than going fast.
But I do remember two occasions when Bruno was mixing it with the Virgin cars in races, particularly in Turkey I remember him overtaking and battling Di Grassi. Something that none of his teammates ever did and with a car that was quite clearly slower than the Virgin.
Bruno was also quite decent in GP2, sure he didn't win the championship, but he wasn't rubbish either. At the very least, he should/could be a good F1 driver of the likes of perhaps Panis or Fisichellla.
May I also point out we currently have a driver who proves you can't always judge on lower formula...Kamui Koabayashi.