That's unreasonable, unless you used an 'out of (the number of games created and have yet to be created)' system. They're brackets, and thus more than one game can fit into each one. Thus, really, the top 5% of games should get it, mathematically. Even if you don't want to use that system, it's still unhelpful for those trying to find out about the game if you lump the 9.5's and the 10's together, which is what will happen.
And, it's impossible to know if it will be the best game of all time, thus nothing, including the best game of all time, will be able to be rated as such, because everyone will be waiting for something to surpass it.
As a side note, good to see you, lol.