FPS games should be listed among the games you buy for the PC.
But not exclusively. There's no honest-to-God-reason why FPS's don't work on the console, lest you bring the PC-centric arguments of the mouse-and-keyboard; to which I say boohoo to an argument over mere control preference.
All the talk of Dying PC games is silly. Hasn't the witcher sold 1 million copies worldwide?
It's one of the few who have broken the million-copy-sold mark. Not many games receive those kinds of sales anymore, save what Blizzard and couple of others put out. I don't think PC gaming is dying so much as receding.
Also what about MMORPGs?
It's the genre that's making the most money right now, at least. If there were suddenly a renewed interest in single player games on the PC then there would most likely be more money thrown into developing games for it.
Would I want to play WoW on a console? With that lousy gamepad?
Why not? It's not as if WoW is that complicated of a game to play. What "lousy" gamepad are you referring to that couldn't handle the game?
Or not being able to customize my UI? I doubt it.
You really can't customize most UI's on most PC games, as it were, short of hacking them.
So yes, there may have been no game with as much depth as SS2 since its release...
Are you sure? That's a rather subjective opinion limited to a person's point of view and exposure. To say that simply ignores the last decade of PC game releases, honestly. I'm not sure how a person would measure how much depth a game has on any reliable scale, but I could rattle off quite a few games that I could see exceeding SS2 in that department. They're not all FPS's either, since you didn't limit the selection to just that genre.
...but does that mean PC gaming is in decline. NO!
Declines happen in different forms, 'bro. If you consider how many truly unique PC games with the depth and stature of Deus Ex, SS 1-2, Oblivion, etc etc, there just haven't been that many released for the PC in the last few years.
If you consider a decline in terms of sales, then yes, there is certainly an example of your decline there. Save Best Buy and a few select stores, PC games don't get the same shelf space they used to in years' past. That's just one reflection of the market, of course, but there's been reporting a pretty consistent slide in PC games sales for a few years now.