Morkus from Orkus
First, there's no way to tell. Are the PCs in example 2 across the continent from where the ranger's family was killed? If so, then it would be less realistic than encountering goblins local to the area that they are in.Here are two scenarios.
1) The PCs leave town, traveling to the north and run into goblins.
2) The PCs leave town, traveling to the north and run into the tribe of orcs that killed the ranger’s family.
Which is more realistic?
Second, that's only one example, so even if both are equally realistic it completely misses the point of what I said. I'll quote it again.
"There isn't a person alive who has every circumstance they encounter meet some sort of personal dramatic need."
So if the PCs leave town and run into the tribe that killed the ranger's family, that can easily be as realistic as the goblins. However, if they then continue on and run into a caravan where the wizard recognizes a guard from his master's tower who disappeared on the night he was assassinated, then continuing on run into a hermit who happens to know the recipe for a potion that might cure the fighter's sister of the magical disease she is suffering, and on and on, it quickly becomes highly unrealistic.
I don't enjoy those sorts of games. If you do, that's awesome. Having fun is the important part of RPG gaming.