What's so wrong about comparing one game to another game?  One game is released after the other and the two share certain elements, so let's compare them.  It sounds innocent enough.  The problem arises when the one doing the comparing can do nothing but compare one game to another.  Red Dead Redemption is just GTA with horses.  Castlevania: Lords of Shadow = God of Colossus's Inferno.  It gets old.  X game enjoys some similarities with Y game in that it does ABC where Y game also does ABC.  There's nothing inherently wrong with that.  Games, like other media take inspiration from one another, they're iterative, they progress from one to the next, it's the nature of many art forms, not just games. 
 
The REAL problem is when a game is so unoriginal that there truly is nothing to say about it other than that it lifts "this" and "that" from certain games.  I hope that game designers continue to be inspired by one another's products, keeping the things that work and discarding the things that don't while refraining from borderline plagiarism and simple copying of their competitors.