I love my dog. Dogs were the first species to be domesticated.
Is your dog friendly?  Are most dogs friendly?
Yes very friendly. Their association with humans have made dogs very attuned to human behavior.
I wonder why other similar animals like wolves can't be domesticated?
There is Intra hybridization among wolves and dogs because their species are so similar, and genetically very close. 
If you cross a dog with a wolf, will the offspring be domesticated naturally?
evidence before courts of law.
Admixture between domestic dogs and other subspecies of gray wolves are the most common wolfdogs since dogs and gray wolves are considered the same species, are genetically very close and have shared vast portions of their ranges for millennia. Such admixture in the wild have been detected in many populations scattered throughout Europe and North America, usually occurring in areas where wolf populations have declined from human impacts and persecutions. At the same time, wolfdogs are also often bred in captivity for various purposes. Admixture of dogs
in the genome. The same process may also apply to other domesticated animals.
In 2014, a whole genome study of the DNA differences between wolves and dogs found that dogs did not show a reduced fear response but did show greater synaptic plasticity. Synaptic plasticity is widely believed to be the cellular correlate of learning and memory, and this change may have altered the learning and memory abilities of dogs in comparison to wolves.
Dog domestication Positive selection Behavior.
Unlike other domestic species which were primarily selected for production-related traits