Sorry for the late reply. I've been out almost all long weekend.
There are ten missions in MS3, right? That's what I read, but I got to mission 5 today, and it read :FINAL MISSION!?!? I didn't bother beating it, but please tell me I haven't spent me money on only five missions. I never would have bought it otherwise. The thing is that Metal Slug jumped out at me the first time I saw it and still manages to impress me. I popped in MS3 for the first time (after having played it in the arcade), and thought, of the new levels I saw "Oh. Oh well." It's just got something missing. It was a riot while doing two-player mode with my brother, but I later returned to what seemed to be the monotony of one-player mode. Now I've experienced a bit more, and I have greater realized the impressiveness of some BG's, but I'm too pissed off thinking it's only five missions long. And MSX is just a bloody rehash. It hardly improved MS2.
About Samurai Shodown II, I once made a summarizing post about this in DolphinLord's club, but essentially SNK destroyed the great, un-paralleded Japanese feel of the origianl.
The music:
SS1's was deep and powerful, original and awesome. It fit the game and backgrounds so perfectly. The music brought out a unique sentiment during each match, whether fighting the legendary Haohmaru on cliffs by the sea, Galford in front of all the sailors in San Francisco on the docks, or Tam Tam in the mysticism of Green Hell in South America, it made doing combat with anybody an incredible treat.
Come SS2, they watered it all down, remixed some tracks (not very well), went from base to soprano, didn't do a good job with the new tracks (except Mizuki's & Kuroko's, I'll admit), and the whole thing made me feel as though they were trying to force the same feeling and auru the music of the original had. I think the best comparison is Kyoshiro's SS1 to SS2 music. Also, what was that "death" music all about after the final slash of the battle?
The Backgrounds
The first time around, SNK combined beautiful colours with their amazing artwork. Take Green Hell. It had lush, captivating colours, fish jumping in and out of the water, mini waterfalls continuously cascading as the battle went on, nice totem polls (which of course could be chopped), the tranquility of Jubei's stage, at a time of year where it appears most aesthetic, Kyoshiro's & Galford's with much more activity the first time around, etc.
SNK reworked the BG's into ugly things, compared to their predecessors. Whether the difference was great (Nakoruru, Earthquake...) or subtle (Hanzo, Haohmaru, etc.), they just went the wrong way with them.
Other
I'm running out of time, so everything else is going under "other." For one thing they shifted from the 'points' to 'wins' system (which meant no more Edo Express Delivery Man throwing big treasure chests of coins, etc.) whereas I have always preferred the points system. Characters were tweaked i.e. Haohmaru's shortened medium (which looks esp. horrible if seen in slow-motion). I somehow prefer unbalanced fighters, no matter whether this works in my favour or against me. Giving the boss a metamorphosing "pet" who comprised about half her special attacks was lame. There were however a few more storyline scenes in part 2. SS1 used the world map. I love fighters that do. It also had the allure of being something new. Blah blah lots of other stuff that could, in full detail, fill up about five pages (really). I'm behind on my uni. work so I won't be hanging around here as often as I used to, but as a rushed version, that's what I don't like about it, and the fact that I spent $200 on the game to make such discoveries.