Which year has the most number of PC games releases?
year refers to release_year; the most number of releases refers to max(count(game_id))
SELECT T.release_year FROM ( SELECT T2.release_year, COUNT(DISTINCT T3.game_id) FROM platform AS T1 INNER JOIN game_platform AS T2 ON T1.id = T2.platform_id INNER JOIN game_publisher AS T3 ON T2.game_publisher_id = T3.id WHERE T1.platform_name = 'PC' GROUP BY T2.release_year ORDER BY COUNT(DISTINCT T3.game_id) DESC LIMIT 1 ) t