This is, hands down, the best lightgun game I've ever played.
It actually introduces the concept of STRATEGY to the genre, something I've never seen. The first few levels are easy, after that, you'll need to conserve shotgun ammo for its stopping power against the fast enemies.
Also, the "shoot leg, shoot head" trick is back from RE4: if you shoot a zombie in the leg, they'll not only fall on their knees, but you'll be more likely to get a critical shot to the head while they're on their knees. Then, there's the fact that you can also throw grenades for AoE kills, as well as shoot exploding barrels, cars and mines. There's also a knifing strategy. At any time you can hold Z on the chuck and shake it to knife enemies in front of you, and if you're quick, you can slash away "hugging" attacks from zombies but if they go to swing at you, you'll still be hit.
I'm only on Nemesis section so far, but the difficulty DEFINITELY ramps up and the "shoot it in the face until it dies" strategy won't work as there are just too many zombies coming at you at once to not start picking away at the knees. The two player is also awesome, but it's still hard enough that you're going to die if you're not careful (and this is on Normal, hard must be a bitch).
I love it, so far, and the narrative with Wesker is also very interesting. You'll be unlocking story briefings and such by shooting lights and other objects in game and then using the action button to pick them up. You'll probably need to go through more than once, but that's alright as the strategy elements will make this easy to go through a second time.