Note: This is a table I employ for personal use when it doubt during an assessment of an article for WP:CVG. This isn't any 'official' requirement for any importance, and mostly used to help me distinguish between Mid/Low and None.

Importance When
Top Never. All Top-importance articles exist already.
High Main characters in important games (Link (Zelda), Pikachu). Companies that have produced multiple award winning games. (Blizzard Entertainment) Games that have influenced their genres a lot. (Super Mario Bros)
Mid Award winning games (Age of Empires 3). Main characters in mid or high importances games (Donkey Kong). Companies that have released a single high-importance game or multiple mid-importance games.
Low Any company that has released a mid-importance game. Any character in mid-importance games. Any game that has been professionally reviewed, and any company that has released multiple of these.
NA The rest.