MS3 - After many years away from 2D gaming, I was just so blown away that the NEO GEO was capable of pulling off the level of visuals and fluid animation that are present in MS3. It's the reason that I wanted to grab a NG console so badly and the reason that I've fallen down the SNK rabbit hole.
MS2 - When I finally decided to grab a NG console I initially went the NEO CD route and my first title was Metal Slug 2. I put countless hours into this one so it's got a special place in my heart.
MSX - MS2 with improved slowdown and variation in levels, I'm in!
MS5 - After constantly hearing that MS5 was a weaker game in the franchise, I just mostly ignored this one. When I finally picked it up, I was pleasantly surprised and have grown to really love the game. When I decided to finally grab an MVS cart I thought to myself "this probably won't be too expensive, after all it's not as good as MS3 or MS2" Fuck was I wrong...
MS1 - Definitely a classic, but I played it after MS3, 2 and X so It didn't have quite the impact that it probably had for most of you NEO GEO vets that were around when it was initially released.
MS4 - Definitely the weakest of the bunch, but at the end of the day it's still a Slug game and in all reality still a competent game. Shit this would have been a classic on any other console.