I heard the XBLA port of Metal Slug XX has some problems that, considering who I heard this from, probably only matter if you're a hardcore nerd who still uses a 4:3 CRT because you only play arcade games. I heard the same about RayStorm HD, except the problem there (part of the playing field being cut off) really does matter.
(Incidentally, you can get a new copy of the original DS version of Metal Slug 7 for the same price as the XBLA port nowadays.)