Whats a fair price on Gears of War, and are Metal Slug 4 & 5 for the xbox rare?

[SNKMat]

Ive been trying to sell Gears for the longest time and no one wants it so whats a fair price? and are Metal Slug 4 & 5 for the xbox rare?

 

[Trenchalicious]

$22-27 for Gears (depends on condition)