The star rating your scouts give you for a player is relative to your squad. If you're managing a decent prem team, most of your players will probably be 2 or 3 stars, In relation to your squad, even messi isnt 2 and half times as good to your 2 star players. Whereas put Messi in a lower league team, say Brechin City, and he probably will be 2 or 3 times better than the rest of your players and will have a 5 star rating.