Also, about the mods, I agree with Vault101. If the game hasn't convinced me on its own merit, then I'm not gonna bother modding it. I'd just stop playing it.
I must say though, the definition of mod seems to be up and down here. When I say mod, I mean a sort of unofficial expansion. Like Nerhim to Oblivion, or the Wanderer's Edition of Fallout 3. Something that modifies the game itself.
Things like CS:S and Dear Esther were just their own games. All that was modified was the engine. And if modifying the engine counts the game as a mod, then damn, half of the games in the world must be mods too, Unreal Engine anybody?