Just like rating or betting on anything, it is more a matter of opinion than it is fact based. When it comes to rating certain things based on the criteria, you can never truly have a completely unbiased event. Just like contests to determine who is the best at something. Or, as in Vegas trying to name the best casino.
Unless you have firsthand experience at every casino, you will not be able to make a true decision without having some assumptions thrown into the mix. Just like rating European soccer players, it is hard to make a decision unless you have seen every one of them at some point play in a match.
Before you do decide, you will need to make a list of your criteria as well as your rating system, so you will better be able to give out fair ratings and then make a true determination of who is the best player is.