Show the game name that has most number of hours played.
SELECT gname FROM Plays_games AS T1 JOIN Video_games AS T2 ON T1.gameid   =   T2.gameid GROUP BY T1.gameid ORDER BY sum ( hours_played )  DESC LIMIT 1
game name that has most number of hours played refers to MAX(SUM(hours_played)); joining tables to connect game names and hours played;