I just played up through the first six levels of the game. Solo, on Serious difficulty.
This is, without a shadow of a doubt, the best FPS campaign of the last 5+ years.
The basic gameplay is the most important part, and they nailed it. It shouldn't be a novelty that, in an FPS game, you click the mouse to fire the weapon, and it goes where you aimed it, but unfortunately we live in a world where it is. Beyond that, though, the movement is appropriately speedy, and the addition of a sprint to the old-school formula is welcome. Reloading was a bit of a question mark, but the way it works is definitely cool - it's not a universal thing, and only affects weapons where it makes sense to, in terms of mechanical game design balance (The Rocket Launcher doesn't need to reload, the double-barreled shotgun works the old fashioned way, etc).
The level design is fantastic; you've got a good mix of big, long, open-arena brawls, tight corridor shootouts, and fights taking place over a big grid network of alleys and buildings, along with tons of secrets to find. The encounter design is just as good - all the old enemies are just as fun to fight here as they were in the original game, and they do a great job of mixing things up so that one simple strategy just won't work. The sixth level in particular is basically a long series of attempts by the game to overwhelm you with mixed waves of enemies. Each 'arena' the fights take place in is different from the next, and each one contains a sort of fight that you've never quite been in before up until that point in the game.
All the weapons are both useful and satisfying: The Sledgehammer is powerful and fun to use, even after you get both Shotguns, either of which could have potentially made it obsolete. The Rocket Launcher can either make short work of the toughest enemies, or mulch an entire group of little guys in one shot, the Mutilator is awesome, and even the C4 is surprisingly useful in places where you can set it up.
On top of all that, the music is great, the game is gorgeous and runs very well relative to how it looks (on top of giving you some Seriously impressive customization in the menus to tweak it the way you want), and the 'story' is actually fairly entertaining - it's deadpan Serious (sorry) almost the entire way through, but Sam is so turned up to 11 and just such a ludicrous character doing ludicrous things that the juxtaposition of him and the gameplay versus all the other characters acting Serious (sorry again) all the time is pretty damn funny - along with the understated absurdities, like Sam just hopping in an old beater of a car with a vanity plate and driving across the desert, to get from one level to the next.
I've got two minor complaints with the game, and other than that, it does just about everything right. First, the pistol is not perfectly accurate. It's got this weird recoil thing where you fire it, where the cursor sways up and to the left, and the bullets don't go exactly where the dot in the middle of your crosshairs is. It's imprecise, and it feels bad, compared with the six-shooters from the original game, especially if you're both moving and trying to hit an enemy who is very far away. Thankfully, it's not really an issue past the first couple of levels - as soon as you get the Machine Gun, the Pistol is no longer your go-to weapon.The second complaint is basically that, while all of the classic Serious Sam enemies are tons of fun to fight, the new enemies are a bit of a mixed bag. The spiders are fine, but the 'zombie' soldiers are bad, and so are the Tentacopters. It basically comes down to: Neither of them should have hitscan weapons, as a major part of what makes Serious Sam work is that an adept player can dodge almost all enemy fire (the only other enemies in the game with hitscan weapons are the Arachnids, which are big, easy targets, and often stationary). And for the helicopter, you shouldn't need Rockets to take it down - it's not an issue in the stage where it's introduced, since it becomes more of an environmental hazard, but the next time one shows up it's definitely more annoying than fun.
Very minor issues, in the grand scheme of things, but still, a few small areas where the game could have done better. Apart from that, though, this is exactly the kind of FPS the genre needs, and this is going right up there on the All-Time Best list.
Such a great and refreshing shooter.
