There is not much to specify for the question, its really simple: Which title is the first game you have purchased on Steam? Was it a good decision? How much did you pay? When was it and what device? You don’t have to answer all questions, this is just a fun discussion to have.
You can check your history: https://store.steampowered.com/account/history/ Edit: Some in the comments pointed out that the purchase history doesn’t go back all to the beginnings of Steam. So if you purchased something earlier, it won’t be listed on your account.
(I reply with my game too.)
Skyrim. I was forced to download Steam to play it. I was on dial up and had just explicitly purchased a single player game not dependent on the internet, and yet…
Then it forced me download the game through Steam even though I had the physical disk right there. I couldn’t complete the download, it was too large.
Modern gaming. Man sounds really frustrating, even though the game is on disk.
I remember having to leave my PC on overnight to download Batman!