Well is it?
I might buy the bundle with all three, or any other game that's $17.04. Any recommendations?
One of the best FPS RPGs I've ever played. I remember paying $30 for S.O.C. when it first came out. All three for under $20 is a steal. It takes a long time to complete and you'll die a bunch of times but it's an excellent adventure.
The reason I find it so amazing to play is the fact that the game is "non-linear", meaning that you're free to travel everywhere around The Zone. And that whichever AI dies really depends on either the game engine or you, especially the behaviour of them, again, based on your input. So upset though that GSC fell apart, meaning that the 2nd make was cancelled and will be remaked. But I heard about the remaked S.T.A.L.K.E.R 2 game based on a different name and I already don't like it.
The STALKER series is amazing. If you buy the game, I STRONGLY recommend you play with the COMPLETE mod. The mod fixes bugs, improves graphics/performance without changing the game in any dramatic way. There is a complete mod for each title, you can find them on the authors blog: http://artistpavel.blogspot.com.au
You can play in order of publication (SOC then CS then COP), however CS could be played last. It's the weaker in the series, but not by much. Have fun!