What people are overlooking is the fact that Goku was able to reach SSJ3 at the time of his arrival back on earth for the tournament. So obviously, his SSJ2 form would be superior to everyone else's. I always assumed the power that Vegeta felt when Goku fought Yakkon, was a hint at SSJ3. But thats just my interpretation.
So, logically, even Vegeta at SSJ2 would be no match for Goku at SSJ3, so that is why he got the Majin Powerup, cause the true difference in there power came from Goku being able to reach abilities of the highest magnitude of SSJ2, because he could achieve SSJ3.
I hope that makes sense. I know the wording is a bit confusing.
Here is a good example of what I mean.
Although Vegeta was a well Established SSJ1, during the Cell Games, His Power was less than Goku's, because Goku had Mastered the SSJ form.
Same situation for the boo saga, just with SSJ2