When Serious Sam first debuted on the PC in 2001 many gamers were quite enthralled with the title. Let's ignore the fact that it featured a really high draw distance for the time making it easy to see enemies coming instead of them just popping up. Let's also ignore the fact that it managed to be very pleasing graphically for its time, although you could put an eye out on those jagged polygons now. As fantastic as this was at the time it just doesn't compare to, what I believe, is the selling point to the Serious Sam franchise: huge battles against a ridiculous amount of enemies.
Nowadays we, as gamers, think nothing of huge battles against dozens of enemies but it wasn't always that way. Back when playing Wolfenstein 3D it would be rare for there to be more than three enemies in a large room. Quake was somewhat the same although at times enemies would be coming out at a rapid pace making it feel faster paced. Doom upped this a bit where you could have numerous enemies moving around at once but they were, more often than not, groups of the same enemy with a few other monsters thrown in (i.e. eight zombie soldiers with an Imp or two).
But Serious Sam developer, Croteam, wasn't willing to settle for this and brought us the Serious Engine. Walking into a room you will sometimes find yourself dealing with one or two enemies at a time with the occasional large group of one enemy type attacking. But just wait until you get to a mini-boss or boss room expecting a one-on-one encounter - That won't hold up for a moment in this game.
An example of this is in one of the temples in Karnak. As you walk into a room, your AI helper NETRISCA, warns you not to fight the odd enemy that is seemingly sleeping on the floor. You have to cross the chamber and get the gun from the other side of the room first. Picking this up you will find that it's a rocket launcher. Most gamers are probably expecting that it's time to take down the boss, and it is, but he's far from alone. Numerous beastly enemies will charge you while a group of humanoids begin firing their guns at you. While you try to dodge the chargers and avoid the bullets of the humans the boss gets up and the giant scorpion man thing begins to shoot at you with a freaking mini-gun!
At first you will find these sorts of fights to be a fair bit overwhelming but its part of the appeal to the title. Learning where enemies spawn in as well as being quick enough to respond to them is integral to getting through the game. If you're not so good with memorizing enemy spawn locations or twitch shooting then you'll find the quick save key to be your best friend. This was all true in the original title and it's just as true now.
As this is an updated version of the old game the graphics are much easier on the eyes, an issue that has prevented many early 3d titles from seeing as much retro gameplay. The bigger monsters all look pretty impressive as do the backgrounds. However anyone who is coming into this expecting next-gen graphics that are designed to compete with the newest, big budget, FPS titles is going to be disappointed. More important than the graphics is the frame rate and even on an older machine with a weak video card, with the graphics set to Medium, the game ran smooth as butter even when the screen filled up with enemies.
One of the things that will put some people off is the difficulty. It's all too common to walk into a room and immediately be attacked by five or six enemies. Then, as you defeat those enemies, new enemies will spawn in to cheap shot you from all angles if you're not careful. It isn't as if you can't combat this by learning where the enemies spawn in and optimize how you handle each of them. Especially notable are the suicide bomber enemies who can get ridiculously frustrating, especially in areas where they charge you en masse.
If you're a gamer who finds that modern FPS are too easy and want a challenge pick up Serious Sam HD. Mixing challenging encounters with interesting boss fights you really can't go wrong. It can be found on Steam or purchased off of XBLA for 1,200 Microsoft points when it hits those respective services later this month.