Darkenend: The workaround is nice, but still would rather get it as a feature instead :D
LightningYu: I'd rather argue that is not an workaround, but the intention behind this whole Tag concept per se. But they simply thought WHY limit this feature, when they can expand it so you can tag however you want. Favorite, or maybe even different Favorite. Favorite-SP, Favorite-MP, Favorite-Co-op... or complete different tags... and your Suggestion would kinda kill this concept... so on my side, i'm kinda against your suggestion..
Also i've to add you also can pin your Favorite Games on the sidebar as well...
I see your point, but why not also add this anyway to the "Recent" page which is kind of a homepage for the launcher? If you don't add any games, it doesn't appear, and if you do, you have a list of the games you want for easy access, it's not about replacing things, it's about
adding them.