I beat Portal 2 last week (a masterpiece by the way and my pick for GOTY) and I got a real Bioshock feel from the game.
I found quite a few similarities between the two games, mostly in their story telling techniques, I am not going to get into them all, but I found many similarities in the way that they convey their stories.
Also the Retro levels of Portal 2 had a very similar feel to Rapture (at least in my opinion), especially with Cave Johnson's voice coming over the loud speakers. Which brings me to another point, I found Cave Johnson to be strikingly similar to Andrew Ryan. I know that the designers said that they didn't have Ryan in mind while creating Johnson but I have to believe that they at least subconsciously drew inspiration from Ryan while creating the character. Of course Johnson was more lighthearted and humorous than Ryan (just because of the nature of the Portal series), but their roles and and what they did in their respective stories/universes seem too similar to be just a coincidence. I am not saying that Valve stole anything from Irrational and Cave Johnson is actually one of my favorite characters in all of gaming, I'm just saying that they seemed similar to me.
What do you guys think? Did you find Portal 2 to be similar to Bioshock at all? I know this topic has been covered on other forums but you guys seem to be the most hardcore Bioshock fans and I am interested in getting your opinion on the topic.