Reorder this list in any way you see fit, highest priority on the top and lowest at the bottom, remove options as you see fit. Clarify why you chose your top or bottom choices, if you want to.
If you can think of any typical game features I might have forgotten, feel free to suggest some.
Achievements
Adult themes
Automation (Place characters, level them up, sit back and watch)
Battle mechanics
Character customization (skill speccing, etc)
Character design (appearance / personality, etc)
Challenges (non-canon special battle levels, ala Bonus Levels for books or the Super Sheep)
Difficulty levels (Casual/Normal/Hard/Extreme, etc)
Drama
Equipment / Loot
Fast-paced cutscenes (Short)
Family friendly themes
Graphics
Humor
In-depth cutscenes (Long)
Interactivity (Spells / skills to cast during battle, ala Azra)
Language options
Moddability / Workshop
Multiplayer
Multiple endings
Music
Pop-culture references, fourth wall breaking
Post-release maintenance (Bugfixes, balance changes, etc)
Post-release updates (Content, story, side-quests, etc)
Puzzles (ala Mysterious Statue)
Real life morality / politics / social themes, etc
Release on other platforms (Consoles / Mobile / Handheld, etc)
Replayability / NewGame+ / Play+
Romance
Side-Quests
Story - Narratively driven (Writer chooses direction)
Story - Player driven (Player chooses direction)
User customization options (EXP, Gold, Speed, etc)
Voiceacting
Worldbuilding (that is, fleshing out the world, it’s history, cultures, etc)
Zombies