Bioshock - take out Armin Shimerman.
Prince of Persia Sands of Time - remove all characterization from the Prince. No voice actor, no story, just a dude running up walls and killing sand beasts.
Fallout 3 - Remove every overland map. All sewers/caves all the time!
Oblivion - Same as Fallout 3
Mass Effect series - Remove all companion interaction.
Deus Ex HR - remove all stealth elements
Dragon Age - Get rid of all those pesky stats, numbers, equipment managing, etc. Make it a good ol' fashioned action game! Maybe we'll get this by the third installment!
Borderlands - Remove every joke. All of 'em.
Portal 1/2 - GladOS. Just remove her completely. Save a ton of money on writing and voice acting!
Planescape: Torment - Remove the dialogue box.
Sims 1/2/3 - No buy/build mode. All live mode all the time!
Japanese dating sim games - Remove the porn. Read for hours! Date the same two sexist characterizations of women over and over without ever getting any! Oh wait...that's Catherine.
Marathon series - Remove the terminals
Saints Row 2 - Remove all those pesky missions/side missions/etc. All open world all the time!
Jade Empire - Remove the martial arts