I don't agree with the best game or best movie or best book or whatever claims because people's likes and dislikes are not uniform. I'm sure there are a lots of WoW, Starcraft and Modern Warfare players for example that would prefer their respective games over Super Mario Galaxy.
If you want to talk about all games from a specific genre then maybe it holds some weight but comparing all games from different genres and declaring one game the best or making a top 10 or 100 or whatever list is ridiculous.