Just for reference, I thoroughly enjoyed this game, and i will give credit where due, but first my complaints. Also i've only played this on hard with one partner.
graphics, meh. though i wasn't playing this game expecting it to break any boundries, or win any awards. intensity wasn't spectacular, as it felt like going from fight to fight rather than continuous survival (acknowledged, this game was not a survival game but i hoped it would have been). I particularly hated the fact that you can switch to any weapon you have unlocked, and especially that if i ran out of ammo in the pulse rifle, i could switch to hudsons pulse rifle and have full ammo. I was disappointed that there are only about three smart guns that can be found (rather that I found, including Vasquez's), and two loaders, meaning if you are playing four player coop, only three can try the smart gun (unless you switch halfway through the ammo box) and two can try the power loader (without restarting levels or checkpoints). The check point "teleporting" pissed me off, when i was looking for dog-tags, and i suddenly teleported to the check point because my partner went through a door. Also i did not particularily like the roller coaster scenes, for example, when you are running from the big alien through the sewers, and he'd lift up a grate and peek inside, or when the queen would break through the glass and peek outside. It felt like a bad haunted house ride... Finally i hated the invisible walls (you'll know them). I also wished they'd done something more with the engineer ship.
before i go on, I would say that anyone can enjoy this game as is, but to appreciate it, you'd have to see aliens first. personally, i watched alien and aliens before it came out, and i LOVED the easter eggs. walking into the hanger bay of the sulaco and seeing bishop's legs thrown aside, the four grates lifted up where newt hid from the queen, and the acid burns through the floor was awesome. seeing the control room in hadleys hope, and fighting in it was also pretty sick, and i think the crown goes to finding newt's dolls head

. I also enjoyed reading the descriptions of all the dog-tags such as (paraphrased) "Private ____ was the first marine to encounter the queen. Surprisingly he survived for a full minute!" The best combat is when you are in a survival situation in confined spaces, such as hadley's hope control room and vehicle bay, and the sulaco's cargo bay, where the aliens are coming from all around. The acid spray was a really cool effect, where if you killed an alien too close to you, you'd take damage from the acid blood. Also, the variety of aliens was pretty cool, where you would be focusing on a spitter or drone, and suddenly a pouncer would get you in one hit (only on the later levels) I wish there would have been more three way encounters between WY mercs, aliens, and marines, but the few there were were (haha! 2x!) awesome.
I have only played the coop campaign, and have not gotten to the competitive play yet so i can not comment on that. So! if you are a fan of the aliens genre, and are looking to blast away some zenomorphs, get this game now! i love the series, and watching a drone explode from a smart gun blast was AWESOME. if you are not a fan of the series, i would recommend waiting for some sales, but definitely get it when it is on sale.