Mario Kart, Smash and Halo 4.

Dark Souls for singleplayer and Uncharted 3 for multiplayer

I don't really play old games. I just get new games, play them extensively over a week or two and never touch them again.

So I guess that makes your first sentence in the OP a dirty lie :P

SimCity 4
Rollercoaster Tycoon 2

Not only are those my 'go-to' games, I never even left them in the first place. That's the beauty of endless games. You can only play a story-based game so many times, but endless games they... never end.
There's actually a third, but since a year or two I 'permanently' switched from the older game to the newer:

Anno 1602 > Anno 1404

Then of course there's the series I always buy a new game from, since like forever, like Super Mario and Zelda. I wouldn't count merely replaying a certain game twice every decade a real 'go-to' game, otherwise I'd have to fill the list with a whole bunch more games.

Smash!

- Thief I & II fan missions (PC)
- Heroes of Might & Magic II and III (PC)
- Commandos (PC)
- Mafia (PC/PS2)
- SSX3 (PS2)

Dead Rising, Final Fantasy VIII, Dragon's Dogma and Gears of War, in that order. I find interesting that three of those are from the seventh gen.

MGS Peace Walker, Saints Row IV and Uncharted 2 are only a few.

On PC depending on mood:
Ultra Street Fighter IV, Battlefield 4 MP, Need for Speed Rivals

I used to play Tekken Tag Tournament 2s MP like crazy on the Wii U

Brawl ever since it came out in 2008. Before that, Kirby Air Ride. Both are still great games to play with friends. Pokemon is also a great fix no matter what platform.

I was hooked on MW3 and Battlefield 3 for a while. I don't really play CoD anymore, but I'll still get on BF3 every now and then to have some fun in helicopters and jets and stuff.