I'm not great at thread titles.
What do you say then? To make it a bit easier, let's go with stuff that's PC exclusive or PC primary--meaning, it might be on consoles, but it might as well not be, since sales/playerbase/whatever is abysmal. So no Dark Souls, in other words, because everyone already knows about that, but Sanctum 2 or Tropico 5 would count.
Not agreeing with limiting selections based on that.
If a person is new to PC gaming I'm going to have her/him play a game that's enjoyable on that platform regardless of whether it's multiplatform or not. Regardless of whether the community is dead or not.
Examples...
Mass Effect 2+3 (now that there is controller support),
NFS Shift (with current hardware the driving experience and visuals are a joy),
NBA 2k15..because it's better than the console versions,
Alan Wake,
Skyrim modded
Red Faction Guerilla
All those are excellent PC titles.
If I have a friend that is new to PC gaming I'm going to be thinking of their best gaming interest.
The only PC only PC games I'm interested in are...
Star Citizen
Company of Heroes
Total War: Warhammer
Freespace 2 HEAVILY modded
Myth: The Fallen Lords (this franchise is why I started to love Bungie, not HALO)
Crysis 1
Warhammer 40k Dawn of War
Best thing about the PC gaming platform is the variety of games available. Something for every gamer style.