Red Faction: Armageddon is not very much like it's predecessor, Guerrilla. The former being a freeroaming, devilishly hard take on guerrilla warfare, Armageddon is very much a bug hunt through dark, linear tunnels. Many of the old systems are here, including the ability to only carry four weapons, geomod, the giant, monster and structure destroying demolition hammer, big stompy mechs, and so on.
There are major differences though, like the difficulty. In Guerrilla, you would die easily and often, but in Armageddon the player's health bar has been notably beefed up to make Darius more of a one-man army. Your main enemy is a horde of diverse, flesh-cleaving alien bugs, there are many areas that are so dark you literally cannot see, the environments, being very linear, severely limit the abilities of the amazing GeoMod system, and the hammer weapon seems to deliberately dash your character past what you meant to hit, which is awful given the third-person camera is so zoomed on the back of Darius' head you can't barely see anything past it in close combat situations, buuut...
The game has a much more meaningful and developed story (read, it has a story this time), a real sense of progression, and a character upgrade system. A drawback to this is the game now relies on several scripted events which can be brutally hard to finish on higher difficulties, unlike the rest of the game, and they really draw attention to the lackluster checkpoint save system. If you hit a checkpoint, you better hope you did everything beforehand to prepare for a coming encounter, because as happened in my case, I did a scripted event and died, reloaded the checkpoint, and discovered the area wasn't fully explored and I hadn't yet purchased necessary upgrades on the nearby machine. I had to re-explore the area and upgrade my character three to four times before I finally got it, which was incredibly annoying. Another section asks you to destroy five buildings, and if you die, you have to run aaaaall the way back down the same hallway again and start over.
These are foibles, though. The game is obviously very high quality, and everything meshes together very well. It tried going a horror route, though, and that basically just means you can't see five feet in front of your face. Being a one-man army also reduces the fear factor, especially when you're carrying high-explosives. It feels as though you're being channeled down a single route all through the game, and there is no room for deviation. Lots of games do this, obviously, but it's really not what I was expecting from the sequel to Guerrilla, which had its problems, but the cramped caverns even limit the usefulness of the structure-rebuilding Nano Forge, which is used mostly to reconstruct bridges and walkways deliberately broken by the development team so you could use it.
I enjoyed the game a lot, but it disappointed me in a lot of ways, given the potential of the various systems that came together to make it possible. It doesn't feel like there's much room for creativity - it's turned into a very solid run and gun, but in replaying it, you'll likely be running the same path you ran before in the exact same way as before, made worse by the fact there is literally only one tunnel to follow from start to finish.