Mainly the controller, XBox Live and Halo.
All this will change next gen tough. The PS4 controller looks actually usable. I'm getting older (36) and while i still play online i don't really "social" all that much anymore on Live (i rarely use my headset these days). I'm done with Halo it's been a fun ride but all good things come to an end. I'm back into PC gaming since i bought a new computer 4 years ago (i'm a web designer i need it for work anyway). The cool thing about PC gaming these days is you don't need to upgrade every year. My close to 4 yo Core i5 750 is still strong enough. My 4GB of ram i bought almost 4 years ago is still enough. I replaced my video card once in the last 4 years (5850 to 670). I don't plan to upgrade my PC until fall 2014 (by then most of it will be 5 years old). I happen to like Steam too games are cheap often you can buy then at 20$-30$. I mostly play all multiplatform titles on PC these days unless it's a really crappy port. I prefer the peace of the room my PC is in (the TV and console iare in the living room). Skyrim, Witcher i play all those games on PC.
Next gen i'll buy based on this.
Exclusive games not avalaible on PC.
Games for kids.
Ability to stay offline for 2 weeks (needed for when we go to our cottage).
Ability to sell used games on eBay or Kijiji (although not sure about this one i might buy the games on PSN or Live if the price is good next gen but it needs to be 30$ or less to buy digital for me).