I'm sorely tempted by Last Light, but I'm also really enjoying Dark Souls at the moment, too.
Punishingly difficult Post-Apocalyptic FPS vs punishingly difficult Dark Fantasy Hack'n'Slash. Decisions decisions...
I played through Metro on Ranger Hardcore mode. No hud, extremely limited ammo, higher damage dealt and received. Very fun and realistic experience.
I hope that the new Metro game has Ranger Hardcore out of the box. Buying it at midnight as soon as it launches. Only other game I've done that with recently was Skyrim.
Still haven't tried Dark Souls. Maybe some day.