Crysis 3
Crysis 2 + MalDoHD 4.0
Metro Last Light
Of those 3, Metro is, IMO, the best game, and Crysis 3 has the most advanced graphics (of any game). The first half of Crysis 3 is interesting enough, but the last half was just so uninspired I quit playing. It's really a shame the direction they took that series.
BF4 has some great looking moments, but unless you're into the MP side of it, I certainly wouldn't waste a dime on it to play the SP campaign.
I don't think The Witcher 2 looks that good. The only time it's actually hard on your system is when you use supersampling. The textures and model quality aren't really anything great - - the artists were just really good at making stuff look good as a whole. 3rd person games also generally keep you from getting too close to the assets to really notice.