Take some games developed and released whichwere improved by an emphasis on product testing.
Gears of War 1, Bioshock - Both critically acclaimed with 94/96% metacritic averages. They were made with relatively smaller teams than a lot of other games released this generation on the same consoles even. They both also had extensive help from Microsoft in terms of testing the games and I know at least in Bioshocks case, the result was a vastly better game. They had issues with late testing and it was a miracle the game turned out as well as it did.
Halo 3: Bungie makes a point of having developers sit in with testers to "Help them understand the issues that players faced and to motivate them to make a better game" Halo is one of the biggest shooter franchises in existance in no small part due to their extensive testing which made the game fun for as many people as possible.
Diablo 2/Left 4 Dead: Games by two of the landmark PC AAA developers Blizzard and Valve. They were tested often and early and in the end it forced the developers to make sure that the games had almost infinite replayability. In Diablos case it was simplified combat and quick rewards which kept the players coming back for more and with Left 4 Dead they were likely inspired by the testing to make the AI governor to give themselves and the end users a different experience every time.
The Sims: Once it was in testing the game evolved far beyond its initial concept, and became one of the best selling games of all time, in a large part due to the influence of the female testers and how the developers created the personalities and relationships of the sims.
And finally on a personal note. One of my aquantainces was actually in one of the DS advertisements for one of the Zelda games, im sorry I forgot which one. When he was filming the advertisement he was playing the game and the developers were constantly looking for feedback from him. They were extremely interested in his user experience even though he had never used a DS before in his life! They were there to do a job but that didn't stop them from trying to get feedback on the game.
One thing which seperates the AAA developers from your typical average developers and shovelware, is how well and how much they playtest their products before release. This is an area which needs extra attention on the Wii so im highlighting it again, its extremely expensive but extremely worth it.
Tease.
