Metal Gear Solid for the Game Boy Color, originally known as Metal Gear: Ghost Babel, is probably the best Metal Gear title nobody's heard of.
You'd assume that since it's in the Game Boy Color, it'd have really ugly graphics. Given the reasonably old handheld it's on, you'd assume that it'd be plagued by the same sort of irritatingly arbitrary enemy AI the first and second Metal Gear game. You'd assume the non-canon story would make the game a pointless waste of time.
You'd be wrong on all three counts.