Starts out nice, but gets boring really fast. This game suffers from seriously lazy game design...
I played and was highly disappointed by Alien Shooter 1 (the previous game in this series) although it was fun at first in the same way this game was fun at first, and thought that Alien Shooter: Vengeance looked greatly improved over its predecessor when I first played it.
In terms of graphics, sound, and the quality and quantity of character upgrades, Alien Shooter: Vengeance is much improved, actually. Gameplay wise however, it's pretty much the same, except for the fact that you have new weapons at your disposal, and prettier armor.
The big problem with AS:V is that after the first few levels, the difficulty goes up -dramatically-, to the point where it's not fun or even -possible- to play anymore. I'm actually pretty good at action games and shooters, but on normal difficulty, I honestly couldn't finish this game without cheating.
Also, after about the midpoint of the game, the designers don't even try to give you new and interesting gameplay anymore. All they do is throw hordes and hordes of the most powerful monsters they have in their menagerie at you endlessly, and these monsters really aren't intelligent or fun to kill. They're just bullet soaks that require a rote amount of strafing and a hell of a lot of fire to bring down. And I don't mean a substantial, but reasonable and satisfying amount of firing. I mean "Zomg, when will this thing die already, it's been 3 whole minutes I'm so #@$@ing BORED" amounts of firing, even with the best weapons. It just gets to the point where it's a huge hassle to fight the bigger beasts (and the swarms of smaller ones reinforcing them) and you just sigh and plow through it just to see what happens next.
Near the end of the game you get the feeling that the developers just stopped trying to make a game with any sense of pacing or inherent fun at all. There's no Rhyme or reason to the aliens attacking anymore, and you really don't need any tactics to win, just lots and lots of patience.
This is not a game like Shadowgrounds which requires some planning and tactics, and rewards you for playing intelligently, using the right weapons, and for learning enemy patterns. This is a game where stupid, tough enemies run straight at you and get stuck on walls because their AI is nonexistent, and you have to shoot at them for a minute straight with your strongest weapon, and you wonder why you're even playing anymore.
Honestly, having played it through to the end, I just can't recommend this game for the same reasons I can't recommend its predecessor: it's very boring and repetitive, and even the visceral and instinctual act of shooting isn't satisfying because the gameplay is so dumbed down and unengaging on even the most primal level, that it just becomes work, and frustrating work at that due to the needlessly high difficulty level.
If you want a fun, twitch-based action game with rpg-style leveling up... I'd recommend Crimsonland or especially Shadowgrounds instead of this game.
Hell, even Quake 4 if you have the hardware and like playing from a first person perspective.
Just anything besides this boring, grindsome mess of a game.