A considerable drop in quality after the slam dunk of the previous 3. The decision to change the visuals of the environments to something 3D makes this game uglier than the previous ones even though it came out later. The lack of auto-fire is also a strange decision (it's the only game without auto-fire in the PS2 compilation), and finally, there are too many enemies that take too long to die, making the pacing very slow, which is a crime for a series that is great in that regard. The boss selection is also noticeably more annoying to face than in the previous games. The saving grace is that it adds another slot for new weapons, but still, it might be the worst Metal Slug.