Let me also add that Bioshock Infinite is a good example of a developer adding replay value with the simple addition of a DLC. There was alot of unhappiness in the Bioshock forums over the lack of a replay system where you could restart the game with your levelled up gear. 2K had always intended to make the game linear so I never had a problem with not having this feature but it would have been nice. However, the introduced a very very good arena system in Clash in the Clouds that let you customise and upgrade your gear and try it out on various maps against mobs and sub-bosses. I never really thought of that game having a particularly good combat system compared to something like BL2 or even the original Bioshock but I came to really appreciate the mechanics on their own without the story. I think the Charge tonic combined with shock and a shotgun has some of the best melee mechanics I have seen. Only zer0 has a better melee system and feel to it. Plus the verticality of the sky rails is something you dont really appreciate in the story mode since you just want to get to the next part but once you get a feel for it, its amazing jumping around the rails like spiderman while shooting and jumping on enemies.
Since this was 2k, I had some hopes that they would implement a similar arena system in TPS where you could go right into boss fights. I think the mutator arena certainly helps but holodome really should have been a Clash in the Clouds type arena that gave direct access non spawning bosses in different flavoured maps and mobs.
