I wasted a significant amount of time playing Doom over a null modem as it was freakin' awesome when that happened as that was highly unusual versus sharing a screen in earlier games. Some of that time I was ahem allegedly working.
Any game in which I ended up getting yelled at by my wife, "When are you ever coming to bed?", would be on that list. I agree with most of the ones in the OP and that have been mentioned.
I disagree with STW2. It disappointed me as once again mythologizing things too greatly about samurai history. It could have been much more. There's some excellent mods of RTW1 and MTW2 which deal with the samurai era. I bet you'd like them more. To me, it's a genuine shame that they didn't release a series of professionally made castle types for MTW2 as DLC. That game is awesome and so configurable, but for some strange reason it became largely forgotten by CA. It's as though they themselves weren't proud of it. It was really dumb that MTW2 released a broken game, for you could never not only enter the keep in the game, but what's more, they didn't bother to relocate the key location within the borders of the keep, nor did they bother to allow the parapets to be manned by the defender. In that, it was largely eye candy.
Any game in which the company was far thinking enough to foster a modding community should be on the list, as this was a revolution in computer gaming. It's why I still like playing Half-Life 2 as well as Civ 3 even after spending far too much cash for now discarded games.Any game in which there's a hardcore fanbase means that there's the potential to make more dough from them by releasing well made add-ons. Even now with Steam, you'd think that some of these older games could find some new life by releasing to the fans much needed things. And we even gave them a steady stream of ideas that were plausible. How difficult would it have been to say have a broader total amount of units for MTW2 so that you could play from the Dark Ages with diverse units through the Renaissance?