Well I just got 4 or 5 hrs under my belt and the game is quite polished, along with being fun. With that said I do think the similarities to RE4 are stretched a bit besides the controls, this game is basically a shoot em up which takes skill. I was kind of upset though, I got to the area where you need to pump gas and was fighting lots of enemies when it freaken froze on me (which is why I'm here and not playing). Some areas that I enjoyed about the game is that AI is relatively intelligent and will flank you, and your teammates actually feel important. The game also has some slick controls and you will be ducking, sprinting, shooting around or above obstacles with little effort! The game also has exciting boss fights (I have only encountered one, the berserker). Another thing I enjoy about the game is alot of story occurs while your playing, like Call of Duty 2!
Now the negatives, the level and enemy design is fairly repetitive and I wish there would have been more thought put into designing the battle areas so cover doesn't look so obvious with conveniently placed baracades. Your ally AI has something to be desired in certain situations (they are great for cover fire though) such as running into the dark (those that have played the game know what is bad about being out in the dark) or sometimes getting way to close the enemies and get in a position where I can't revive them. In addition to that on more than one occassion I will call for them to regroup and no one comes! One other area is that it is hard to find weapons to pick up, I know they want to keep things "real" by not highlighting weapons or ammo dropped, but one time I accidently traded a shotgun for my machine gun and I couldn't find my old gun!
Another thing is that regardless of how reloading was advertised it is not what I would call innovative, it is basically hit the button when the white bar is in the darkened area of the reload bar, is it fun to use? Yeah but I'm not sure I would call it as something extremely innovative. Also the game itself is pretty standard, it really does nothing new but like I said to start with its relatively polished and above all else FUN. Which brings me to yet another problem, the game is pretty much formulaic, move from area to area, shoot hordes of enemies, repeat (at least the emphasis on cover makes it relatively fresh) One final problem (at least of what I can think of) are the visuals, I think they are overrated, yeah the models look great but the levels are pretty constricting and textures repeat ALOT, not to mention that it does a poor job of boundaries in that you will run into invisible barriers at rubble piles or in areas that it look like you could jump over a wall (Or jump to a place!). The levels definately should have been more interactive and avoided having places that you know you could get to if the game was real life, but you can't in the game (I know in real life I could climb up a rubble hill!). I dunno maybe I'm just spoiled by PC visuals!
Overall like I said the game is definately a good game, that is one of the, if not the best action/shooter game out there. But I don't see myself wanting to play through the single player again along with the fact that I wouldn't consider it GotY material though based off the single player which doesn't have a heck of alot of depth and some of the flaws I mentioned.
So far I would give single player an 8/10.