Amazing visuals and lag-free gameplay and programming that push the Sega Genesis to its very limits, hence the title screen quotes "VISUALSHOCK! SPEEDSHOCK! SOUNDSHOCK!", "NOW IS TIME TO THE 68000 HEART ON FIRE", and "FOR MEGADRIVERS CUSTOM".
25 stages that each have their own unique and difficult boss fights.
A great story, involving a redeemed crime lord fused with a child to stop Scarlet's current boss, Xi-Tiger, from killing all of humankind.
Fast-paced and exciting gameplay, so much that you can use your own dash as an attack and have 4 slots for different combinations of weapons.
Despite being rushed as mentioned in BQ#2, unlike Sonic '06 and Balan Wonderworld, the game was released in a very good condition, and the game is still amazing.
The extremely high difficulty does not make this game casual friendly, even on the easiest setting!
According to this YouTube video by Daniel Ibbertson which described the history of the game, Alien Soldier was rushed; it was supposed to have 100 bosses and other features, but they were cut from its final release since the Sega Genesis was soon about to be phased out by the Sega Saturn. This probably might have been the reason why Alien Soldier was exclusive to the Sega Channel when it was originally released in North America.
Mean Machines called it "a real gameplayer's game", citing the unrelenting waves of enemies and high difficulty. They noted how Treasure was beginning to establish a pattern of good games, and called Alien Soldier a modern classic.
Frank Provo of GameSpot reviewed the Wii Virtual Console release in 2007, citing the excellent graphics, sound, and general intensity of the game. He noted initial difficulty adjusting to the controls and game design. However, once accustomed, he said, "you start totally feeling what it must be like to be an army of one trading firepower with some of the universe's largest, most elaborate creatures. That's a great feeling."
Dan Whitehead of Eurogamer described the game as "manically-paced" and "bizarrely creative" while also providing a disclaimer that it's "really hectic and difficult if you're not into this sort of thing."