The game that started it all (screenshot wise) for me. It had such an impact. I pretty much became obsessed with it, to be honest. The storytelling and atmosphere of the game was so dang good and the art direction was, in my opinion, perfect. More than any other game, it caused me to slow way down while playing so i could take every tiny detail in. And even after numerous playthroughs, it still wasn't enough. I had to know what the Rapture looked like from the outside. This pushed me to get it on the PC so i could noclip/freecam outside of the levels, which gave me the opportunity to explore the game from a different perspective. And that led into taking screenshots, which in turn led into experiencing games in a whole new way.
This gallery's quality is all over the place (composition, sharpness, contrast, etc) since it has shots going back all the way to 2007. It's nice to have a lot of them in one spot though, blemishes and all.