Trying to complete the underground subway level by yourself is solid. It took me ages to be able to shoot those trains in time before they squashed me. Also, the developers of the Metal Slug franchise are an absolute godsend to the gaming community. These games are all fucking amazing. Also, check out in the hunt. Pretty sure it's from the same team.
MS X this is just an enhanced version of Metal Slug 2. I don't plan on playing this game any time soon. I'll check out this Pomping world after I finish my playthrough of Super Mario 3D Land. Thanks for watching!
Metal Slug 1 only has lags when there are too many units in a single frame. However, Metal Slug 2 has prominent lags in the overall game due to fps being capped to 30 frames only. That's why developers had to release an enhanced version called "Metal Slug X" which fixed the lags and also introduced some new weapons and firearms.
Supposedly the team only tested the game on their own hardware which was much better than the arcade hardware. When they released it for arcades it became very apparent what the problem was so SNK reworked MS2 and released MSX.