For the record......

C&D is NOT at all like metal slug and any other platform shooters... First off it's not even a platform game it's a 2 1/2D side scroller. Secondly the weapons in it are bonus weapon items which have been around since the double dragon games. If you don't have at least one gun around all the time then technically it's nto a shooter. As for it being better than metal slug, it's certainly too different a style of game to make that comparison. It's like saying robocop is better than pacman...... it's merely personal opinon since you can't compare those games.
Also for the record... (here I go again)
The metal slug series is NOT like any other platform shooter. First off this was the first game of it's type to impliment moving bosses at the end. It may not seem like a lot, but for it's time it was a huge breakthrough. The only game prior to it that even compared in terms of gameplay was contra. It surpasses contra in the following ways: (All other platforms prior to metal slug behaved like contra btw.)
#1 Gradiated backgrounds. In metal slug you can actually climb over the sand bags instead of jumping over them like an idiot... making yourself more open for bullet-fire.
#2 The bullets actually move at a more realistic speed. Prior to this all platformers had really slow moving bullets so you could get out of the way after it's been shot. With the exception of speciality weapons and bosses, this is not the case of metal slug, making it a much faster game.
#3 A true secondary weapon. Now I know what your thinking, "that's nothing new." But in this case it actually is. Prior to metal slug all secondary weapons were another gun... which might have a different firing pattern, but it was still a gun. With the addition of grenades that actually arch, it added a new gameplay dynamic in that you could arch a grenade over a bunker and shoot at a guy on a tower while you jump to throw it.
#4 The great ai. Now I know the mslug thugs aren't increadibly smartbut think about it. If you jump over a bunker they will eventually follow. You jump down, they jump down. You climb up so do they. before mslug all generic charcters simply ran back and forth on thier own little platform and that was pretty much it.
#5 The great timing. Experts say that the reason mario became so popular is the great pacing in his games. The same is true for metal slug. The pace of everything is perfect. It's just enough to still seem exciting and yet slow enough to where you do get frustrated.
Metal slug is the last of the platfrom side scrolling shooters and for good reason. It is simply the best out there. It's the ultimate evolution in the genre, it can't be taken any further. That's why all side-scroller fans agree that it's the best. Yeah there are some similarities, but to compare it to a normal side scroller is like comparing quake to wolfenstein.... it's evolved way beyond what the older ones were.