This is an edited excerpt from a post of mine from the thread "Im i the only one that thinks d3 is amazing?" on the Diablo III General Discussion board. But I think it's an idea that should be read by as many 'haters' as possible.
I think that a good portion of the people complaining about the game, are just victims of age. Tastes change. When I was little, I used to run around the yard playing imaginary war with my neighbor friend, or play with hot wheels cars on the kitchen floor. But, at age 23, that stuff just isn't fun anymore. And with 11 years between D2:LOD and D3, plenty of time has passed for series veterans to grow up. So, I wouldn't be surprised if a good half of the people who think D3 is trash compared to D2 are teenagers and young adults whose tastes have changed. They just don't know that it has happened.