You might want to also get some of the deals of good games, for Instance I think you can get both Bioshock and Oblivion for a good price in one package. Or some of the game of the year additions which include bonus material that can save from having to download extra costing content.
From the sound of it you might like 'The Darkness', it first starts as a generall shooter, but after a while it changes from just a mob war to a monster creeping in the dark being a horror. The big difference to simular games is that you are the horror and gain the powers among sending out demons and stabing others with tenticles. It also manages to have a great story and deliver it in a way few FPS's can, also if you are familiar with Witchblade , this is set in the same world.
Also if you are a fan of being able to sneak through the dark, picking off enemies aswell as use of knife and guns then I might also recomend 'The chronicles of Ridick, made by the same company as The Darkness. The 360 released an upadated version of Escape from butcher bay, that was prevously on the Xbox, whith another story called the dark athena. it has praised that it still compets very well, and if you havent played the first one or enjoyed the movies, can be extra good choice. The game includes a good story and an aray of characters that Ridick comes across as he tries to make his way to freedom.
You mentioned you like the sound of 'Dragon Age', I am playing that now and I am enjoying it, a simulary good game is 'Mass Effect' which is also made by Bioware, that is well known for making good RPG's. And really do a good job at allowing players choice have an influence on how it is played. Infact I think Mass Effects 2 is schedueled soon and will also allow carrying character's stats from the first game to the second.
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Through dream I travel, at lantern's call
To consume the flames of a kingdom's fall