Retrieve game details that their level's value is higher than 1/10 the sum of guilds levels
Assuming the Guild.gName = Game.Name, I think you are looking for something like this:

select
    ga.Name
  , ga.MaxPlayer
  , ga.levels
  , ga.uName
  , gu.GuildsLevels
from Game ga 
  inner join (
    select gName, GuildsLevels=sum(level)
      from Guilds
      group by gName
      ) as gu on ga.Name   = gu.gName 
             and ga.levels&gt;=(gu.guildslevels*0.10)