Guns, tanks and loading. A whole lot of loading.
All 7 games play exactly the same way: Equipped with your infinite-ammo pistol, you must go from the left side of the screen to the right, killing and destroying anything and everything that comes your way. You may come across Prisoners of War which, when rescued, will bestow you with rewards, from mere points to limited-ammo weapons, like machineguns, flamethrowers or shotguns.The enemy comes equipped with all manner of destructive vehicles, so it's only fair that you come across vehicles of your own in order to lay waste to the enemy. They are fun, short, arcadey games.
As for the individual games...
Metal Slug 2 is a complete enhancement when compared with 1. New weapons, new vehicles, new characters and the addition of transformations! It's a fantastic game that is sadly plagued with slow-down and the new loading times between screen transitions and even when selecting your character.
Metal Slug X is a remixed version of 2 of sorts. The stages have been entirely recolored, enemy placement has been revised, and you will find new or different vehicles in new places. It also fixes the slowdown that was so invasive in Metal Slug 2. But SNK wasn't content with just that, oh no, there're new weapons, like the enemy chaser, new enemies, like the zombie dog, and Super variations of weapons! It's more than just a 'remix' of 2, it's more than a 'fix', it makes Metal Slug 2 completely obsolete. Sadly, this version has the same Loadin Screen issues as the Metal Slug 2.
Metal Slug 4 was the first game in the series not made by SNK, but by Playmore, and it shows. Tarma and Eri got the boot in order to make room for Trevor and Nadia. There's a new weapon, dual machine guns and, thankfully, vehicles now self destruct if you press R1 instead of shoot+jump, which is so helpful. Besides the two newcomers, which are palette swaps of pre-existing characters, the bosses and a very few amount of new enemies... everything in this game is reused from previous games, heck, the stages look as if they were assembled from pre-existing assets. It feels lifeless, like they weren't even trying and just wanted to pump a new game just because. At least it kept the alternate routes introduced in 3.
Metal Slug 5 adds the Slide maneuver, which isn't needed or particularly helpful but is fun to do. It adds nothing new to the formula besides new enemies and stages, which is more than Metal Slug 4 can say for itself. At this point, this is just more of the same, and if Metal Slug wanted to remain relevant, it was gonna need to shake things up.
Disappointingly, Auto-Fire can't be turned on for this game, so it's back to mashing. At least now you can store up to two special weapons... albeit they are lost upon dying. I didn't seem to come across alternate routes, which is rather sad, and they removed the sliding, which I really liked! The Final Level is kind of a drag as well.
All that said, this is the only game without intrusive loading screens, which is fantastic, and as a whole, it's a great addition to the franchise and exactly what it needed in order to rejuvenate the series.
The sad thing about this collection is that it's mostly made up of great games, but while entirely playable, this are undeniably sub-par renditions of these classics. Trust me, the loading screens are very short, even if frequent, but you can get used to them, but that still makes them inferior to both their Neo-Geo counterparts as well as the stand alone home releases.
8.0 out of 10