It would be nice, but no, I don't think that the world would be a better place.
There are the innocent (though sometimes selfish) wishes:
"I wish I had a million bucks!"
"I wish I was a princess!" (to all of you 6-year-old girls at heart)
"I wish that chocolate wasn't so fattening."
"I wish that somebody would love me."
"I wished that everyone loved God."
And altruistic wishes, which are a great thing:
"I wish that there was no such thing as cancer."
"I wish that everyone was nice to everyone."
"I wish for world peace."
"I wish that there is no such thing as AIDS!"
But there would be malicious wishes:
"I wish that this famous person would dump their wife/husband/girlfriend/boyfriend for me."
"I wish that this person would die."
"I wish that I would die."
"I wish that my parents would jump off a cliff."
And horribly bizzare wishes that would cause disturbances:
"I wish I was an Oscar Meyer Weiner."
"I wish being a Republican was a crime."
"I wish that aliens exist."
"I wish that Britney Spears would vanish."
"I wish that I knew what was inside Area 51!"
"I wish I had [superpower]."
"I wish that I supreme ruler of the world."
And then, someone would do it. They'd wish the ultimate terrible wish.
"I wish that everyone would go away forever and leave me alone!"
And everyone, including that person, would go away forever. No more people. No more existing. No more anything.
So, yeah. It would be a pretty bad thing. SOME wishes would be good, but the bad outweighs the good.