I've been replaying Metro 2033, and while researching similar games, Hellgate: London kept cropping up - I've heard it's good, but not done any more investigation other than googling a few screenshots. What time period is it set in? I've seen screenshots of people wearing cyberpunky medieval armour. What's the gameplay like? I think I've seen first and third person screenshots.
Another game is Killing Floor, again I don't know much about it but I think it's a post-apocalyptic shooter set in the UK, right?
Also, I bought the S.T.A.L.K.E.R. SoC and CoP pack in the steam sales, just installed SoC, is it worth getting Clear Sky as well?
Hellgate london:
1. mostly stable.
2. generic rpg with a generic interface. Gameplay is much more fast-paced than WoW in PvE and has much more fast-paced gameplay in general.
3. Gameplay is reasonably challenging.
4. Unless you're korean, no multiplayer.
Recommendation: give it a rent to see if you like the single-player gameplay. Lack of Multiplayer support for western gamers may diminish the game's longevity for you. Hellgate London is a meh title. Nothing special about it really.
S.T.A.L.K.E.R Clear Sky:
1. The most unstable games in the series.
2. Kinda bridges the C.O.P and SHOC gameplay. Playing Clear Sky would give you a better chance to learn the ropes of the clear sky changes carried over to C.O.P. C.O.P is the only game in the series that has high-powered enemies as a consistent threat throughout the entire experience. Clear Sky and SHOC both start you off with less challenging enemies than C.O.P thinks is a good idea to have roaming around in the first area. Clear Sky and C.O.P share the new artifact hunting system and the threat of blowouts. C.O.P however kinda expects you to already know how to deal with it.
Reccomendation: Buy if your really in love with S.T.A.L.K.E.R. Otherwise, stick with C.O.P and do not buy Clear Sky if you want to enjoy the changes to the gameplay clear sky made to the series.