BioShock vs Portal 2
BioShock
BioShock is one of the most highly acclaimed steampunk-themed shooters that has a very interesting twist - your very character's DNA can be modified through the use of a selection of plasmids and a special resource called ADAM, allowing you to have superhuman abilities which will serve you well, sometimes more so than the weapon you wield, in your adventure through the fallen underwater city of Rapture. Aside from the many violent mad men (a.k.a. Splicers), the game also provides players with challeging encounters with the iconic Big Daddies and Little Sisters.When it comes to non-military-styled shooters with an intensely immersive storyline, BioShock is among the handful of the "best of the best" (which includes the Fallout series, the Borderlands series, the Deus Ex series and others). The game boasts of having a rather dark storyline that actually challenges you to think about it in a more in-depth way; to link all the clues together to get the complete narrative that is surprisingly a lot more engaging that you'd expect.
2K Games has just released the remastered version of the very first Bioshock last year and if you can get it on Steam, you really should. The very unique experience it can offer you is very well worth the cost.
Portal 2
Portal 2 follows in the footsteps of the award-winning original while continuing the story of Chell and Glados. Now with both single player and a 2-player cooperative mode, Portal 2 ramped up its game with a plethora of new, challenging puzzles, a storyline that's a lot richer than before, and more advanced and realistic physics that will govern your gameplay. Interestingly, the game also includes editing tools, allowing players to create their own puzzles which can then be shared for all to enjoy.Portal 2 is definitely a much better game in the series and if you fancy giving this franchise a chance, you might want to jump straight to Portal 2.