I think this series has seriously gone downhill. If the second game was more like Alien Breed 1, then the third game is pretty much like Alien Breed 1. There have literally been no new additions to these games. The only things that are different are either very trivial or are more of an annoyance than a feat.
Just as the previous installment, in this one some of the weapons have been changed around too. Once again, the first three weapons are the same but for the last two, now we've got an Electric link gun and a Project X. They're not bad at all and can be useful a lot of the time, but despite that, I still found my self using the original 3 a lot more often, but probably depends on the player.
The game also tried to a little gimmicky stuff. In some areas the game takes a more over-the-shoulder perspective. Those parts are quite nice for eye-candy purposes as they break the norm and make you fight in a slightly different fashion. However, most of these parts tend to have fixed camera angles, and hence if you change direction, you often don't see where you're going. It's still a nice addition, but I wish it didn't restrict you with fixed camera problems.
The story was never going to be one of the strong points of the series, as the player still walks through the same dark, semi-exploding corridors, from one part of the ship to another, activating computers and other systems. I would, however, point out that the main villain takes up a bit of a spotlight in this installment as we get to find out a lot about him. I'd even say he becomes more likable than our muscle-head of a hero.
Overall, all of these games are literally identical to each other. In fact the quality of the entire series has gone down in my eyes because of the fact that each new game was the same as the last. Even the Steam achievements are identical in all three games. If you want to get maximum enjoyment out of this series, then I'd recommend you play only one of the games, and not all three. Any of them will do, although the first is probably the best.