bystander :
The original Titan is no longer a top performer. It is respectable, but it is beat out by the 980ti, 980, 970, 290x and several others. It is respectable in performance, it just is no longer top tier.
While I did not write that a 980ti is faster than the Titan X, it is true with aftermarket versions. Titan X only comes in reference design, which does not have the best cooler, nor does it have the power phase improvements that aftermarket cards sometimes come with. Here is one such card that beats the Titan X: http://www.techpowerup.com/reviews/MSI/GTX_980_Ti_Gaming/30.html
"beats" is a relative term. The GM 200 is the same in the 980 Ti and Titan X. Except, the 980 Ti is binned lower. The only way a 980 Ti can "beat" the Titan X is when it "cheats" in a sense. Look for yourself. Every review of a 980 Ti "beating" a Titan X, has a custom PCB and is overclocked, meanwhile the Titan X is not overclocked. There is a big difference.
In other words, any 980 Ti with a custom PCB and overclocked will beat a Titan X. But when you overclock the Titan X it beats any and all 980 Tis even when they are overclocked.
Case in point. I happen to own both. My Gigabyte G1 980 Ti is clocked at 1550 Mhz compared to my Titan X clocked at just 1400 Mhz. The Titan X "beats" my 980 Ti in every benchmark. Every single one.
Add to that, the voltage can be unlocked and the bios flashed on the Titan X. With it being a higher binned chip it will start to pull away even further from it's "gimped" 980 Ti sibling. Check for yourself. All the overclocking benchmark records are currently held by Titan X cards.
If money is no object, Titan X is the single most powerful card available today. It's price to performance is another argument all together. Add to that, 12 GB VRAM and it will certainly push games longer than any other card presently available.
Case in point, Shadow of Mordor and Batman Arkham Knight use more than 6GB VRAM and will bring the 980 Ti to its knees. I can play Arkham Knight in 4K today and achieve console level frame fluidity. The game uses over 7GB and sometimes as high as 9GB in 4K resolution. I get none of the frame freezing on the Titan X rig compared to my 980 Ti rig. The issues with Arkham Knight are well documented. Just search for Arkham Knight PC and read all the negative reviews and complaints. A card that can play that game in 4K today on PC despite all the well documented complaints is testimony in itself.
Update: 980 Ti KINGPIN edition now holds the world record. So that is the card to get. BE warned though. It's listed at 849 dollars US. 150 bucks cheaper than the Titan X. But the price you will pay will be closer to the Titan X. That's provided you can even find one available for sale. Head over to EVGA's website for more details.