The Ultimate Doom is updated version of the original 1995 Doom with a fourth level added. You play as marine that assaulted a superior officer for ordering his soldiers to fire upon civilians. As punishment, you're shipped to the home of the Union Aerospace Corporation, which is a conglomerate with radioactive waste facilities on Mars, which has two moons, Phobos and Deimos. As the story goes "with no action for fifty million miles, your day consists of suckin' dust and watchin' restricted flicks in the rec room."
However, as it turns out, the military has been using the remote facilities on these moons to conduct secret projects that use inter-dimensional Gateways. These have become unstable and when Mars receives a garbled message from Phobos that something evil is coming out of the Gateways and Deimos has disappeared entirely, your combat troop is sent to investigate. Ordered to secure the perimeter while the rest of your buddies go inside, you can hear the screams of combat through your radio, but suddenly there is silence and it appears everyone is dead. With only a pistol, you need to get your hands on some heavy assault weapons. As you approach the base, you can hear strange animal-like growls echoing in the corridors.
Although you are not given this background story for Doom in-game, it's provided in the accompanying manual which, for steam copies, can be found within the store game page. Ultimate Doom consists of the first three original episodes plus the addition of a fourth. Each episode has several levels and the goal is to kill the demon hordes and reach the exit of each level. Combat in the first three episodes is relatively easy, but the fourth cranks things up a few notches. It was designed specifically to be far more challenging and you will notice the difference. There are puzzles to solve, secret areas to find and gateways to teleport through. You can access a map feature, which I found rather unique as it actually draws in the rooms and corridors as you traverse them. This enables you to see where you've been, but not where you're going unless you find a computer map in your travels that shows the entire level. Between episodes, there is also a short written update on the story.
Doom set the standard for the typical weapons arsenal in first person shooters: pistol, assault rifle, shotgun, chain gun, rocket launcher, etc. as well as your good old fists. Health kits, ammo and a wide variety of power-ups are fairly abundant throughout. Among the obstacles are demonic monsters, toxic slime pits, traps, switches and locked doors, which require finding a keycard. The labyrinth of corridors and rooms on each level make the environments constantly interesting to explore, but on the down side, no new creatures are introduced. The secret areas are not marked or obvious, so my advice is to click on a lot of walls as a matter of course.
The boss fights are unfortunately lacking and unremarkable. They are only challenging from the point of view that one hit from them means you are dead, so there really is no fight. These situations often involve finding the sweet spot where you can avoid being hit while firing on the boss. After the final boss is destroyed, a hidden doorway back to Earth opens up and in the final cut scene, we see flowers and bunny rabbits. As the camera pans, it reveals a burning city and a bunny's head impaled on a stake. The demons have invaded Earth, paving the way for Doom 2.
If you think Doom and Quake are remarkably similar in gameplay, you would be right. They were both developed by id Software using the same 3D graphics and engine and both play like a dream on the PC. Originally, the first 9 levels of Doom were released as shareware, highly popularizing this type of game and creating a boom in first-person shooters. The ability to modify the game through files called WADS (Where is all the data) became another popular aspect as the first level editors were released in 1994. The distribution of the WADS allowed people to update the graphics, create new monsters and fix any bugs as well as make entirely new levels.
I opted to play this game with the source port GZDoom, which not only updates the graphics, but allows for the re-mapping of keys. Although there are all sorts of other options added in the menu, I didn't use most of them. I chose this because I'm not so nostalgic as to enjoy highly pixellated graphics and I'm used to playing with certain keys. Source ports are different from mods in that they supposedly don't alter the actual gameplay. The last four screenshots are a sample of the game without the source port.
Doom 2 introduces some new types of monsters and all new maps, but basically it's just more of Doom. There are no major technological developments, graphical improvements, or substantial gameplay changes. One weapon was added in the form of a super double-barreled shotgun. Maybe I'm just getting doomed out, but at level 27 it's all starting to become a blur.
Final Doom Nothing new here either. There are two episodes to the game, respectively called TNT Evilution and The Plutonia Experiment with the latter being harder. Considering that there are literally thousands of other Doom levels that can be downloaded for free, there is probably actually no reason to buy this unless you are an avid collector. As the story has never played an integral part of these games, you won't be missing anything. Unless you are seriously a Doom fanatic, you might want to give yourself a fair amount of breathing space between Dooms. Doom 3, however, is a different kettle of fish.UPDATE Oct 2015: Doom 4 is scheduled to be launched sometime in 2016.