Are half-blooded Saiyans stronger than pure-blooded Saiyans? I'm wondering if half-blooded Saiyans are stronger than pure-blooded Super Saiyans? Like how half-blooded vampires are stronger than pure-blooded vampires.
According to Wikia


The offspring generally possesses the strength of the Saiyans and develops abilities far more easily than Earthlings.
Hybrid Saiyans possess the potential to become Super Saiyans but it is unclear how many generations can separate a hybrid  from their Saiyan ancestor before the transformation becomes impossible.
It is unclear if these hybrids possess a naturally greater potential than their Saiyan parents. Gohan repeatedly demonstrated a hidden power that, when harnessed, made him more powerful than even Goku or Vegeta, and when he and Goku trained to battle Cell. 
It is unclear if Hybrid Saiyans may become Super Saiyan faster than pure-blooded Saiyans. Gohan become Super Saiyan at  the age of 11 (9 in the manga). Trunks and Goten were able to make the transformation to Super Saiyan at a far younger age than their fathers, at the age of 8 and 7 respectively.
Further, it is unknown if quarter Saiyans, such as Pan, have a lesser potential than half Saiyans or pure-blooded Saiyans. Most importantly, Pan doesn't transform into Super Saiyan, or it's simply because it is harder to transform for females.



According to my knowledge


In the series, either Goku, Gohan or Future Trunks said that half-blooded Saiyans can transform into Super Saiyan earlier than pure-blooded Saiyans because they possess the Earthling's rich emotions and feelings. Since turning into Super Saiyan requires to be highly emotional, this makes half-blooded Saiyans transform at a very young age.
I don't think it's because half-blooded, so it's weaker than pure-blooded. For example, Goku passes down his ascendant gene to Gohan, so Gohan has the potential to surpass Goku. It takes training. In Cell Game Saga, Gohan trains in Hyperbolic Time Chamber together with Goku, and he ultimately surpasses Goku. If he trained non-stop like Goku, he might have become Super Saiyan God.
Obviously, the more generations, the lesser the Saiyan's blood in their body. I don't know if that works with Saiyans, but in real life it does. In the 10th generation, or roughly 300 years later, the Hybrid Saiyans will become 1/1024 Saiyan-1023/1024 Human. As you can see, Hybrid Saiyans are not likely to transform into Super Saiyan, but they still possess enhanced strength.
Maybe someday either Bulma or Bulla invents a device that can release the hidden potential, making it easier to turn into Super Saiyan.