WITH Points
     AS (SELECT Sum_Points = SUM(points) OVER (
                                 partition BY email),
                Games_Played = COUNT(ID) OVER (
                                 partition BY email),
                Average_Points = AVG(Points) OVER (
                                 partition BY email),
                Rank = DENSE_RANK()  OVER (
                              Partition BY email ORDER BY Points DESC),
                *
         FROM   dbo.Game)
SELECT Ranking=DENSE_RANK()OVER(ORDER BY Sum_Points DESC),
       Name,
       Points=Sum_Points,
       Games_Played,
       Average_Points
FROM   Points
WHERE Rank = 1
ORDER BY Sum_Points DESC;