Some people say this because they really like the code - the modes, the way the drops work, and the nice touches on the LE/Premium like the walker bombs. Basically, the code took a game with a layout that wasn't incredibly appealing and took it next level.

Other people prefer other games, and wouldn't like the code.

basically it's the same as every other pinball machine ever made. You can't really directly compare the code between all of the games you mentioned, because, for instance, having drop target code on SM or Metallica would be pretty stupid, since those games don't have drop targets.