I’m pretty skeptical myself. At this point, they don’t HAVE this plane. What they have shown is a prototype of an airframe with a lot of promises about what it is going to be in the future.
The airframe flies, but at this point, that’s all anyone knows. We don’t know how stealthy it will be, we don’t know if the promised avionics are going to perform as they claim, we don’t know if it is going to be as cheap to build as they say, and the timeline they give on development and deployment of this aircraft seem awfully optimistic to me.
Even if the design, stealth, avionics, etc., all work exactly as advertised (something I am also skeptical about), to build these things in the numbers they are talking about is going to require many new factories to be built, hundreds if not thousands of skilled workers (many of which are going to have to be trained from scratch) and all the ancillary infrastructure that accompanies a program of this magnitude — schools and hospitals for the base workers, commissary and exchanges, etc.
Given the state of the Russian economy and looking at other Russian defense programs, such as the conversion of the Gorshkov for the Indian Navy (way over time and budget), I just do not see this bird as an immediate or even near future threat.
Russians are master bluffers. I won’t say this thing is a complete bluff, but...
Let's start with the SU-35, the best Russian fighter, as the benchmark. The SU-35 is a highly maneuverable, has great-to-astounding fuel fraction/twr/wingloading, a powerful radar, great range with favourable supersonic persistence, and very good avionics. The weapons it carries are also very capable, both in the short range (IIR missiles), long range (the AMRAAM-ski), and very long range (the AWACS killer missiles). It is a major threat to any legacy fighter (the F-16s, 18s and 15s), and the only fighters that give it a match are the new-advanced iterations of the F-15 (eg the F-15K) and the EuroFighter Typhoon. (Obviously the Raptor is significantly much much much much better).
Now, let's look at the PakFa. If it is better than the SU-35, it will be the second best fighter in the skies (after the Raptor). All it needs is to be better than the SU-35, a plane that (note: Western) sources consider to be totally and thoroughly formidable.
The PakFa will be able to supercruise, have better fuel fraction and TW than the SU-35, have higher maneuverability, far greater supersonic persistence, far smaller RCS signature, much better avionics, and a mix of radars (a main X-band AESA in the nose, a rear-facing X-band AESA, 2 L-band AESAs in the chin, and 2 L or S band AESA radars in the leading wing edges ....the longer wavelength L AESA would not be effective against a high stealth plane like the Raptor, but against the F-35 JSF, which is optimized against the X-band, it may be another story). The weapons being developed for the PakFa are evolutions of what is currently present, meaning a really effective short range missile, and a really effective long range missile (in the class of the Meteor BVRAAM carried by the Typhoon).
Basically, it will be better than the SU-35.
Does that make it a Raptor killer??? Heck no, the PakFa is not a Raptor, let alone a Raptor killer. However, it was not meant to be. It was primarily to provide the Russians and Indians with something that would be vastly superior to what the Chinese (the major threat to both India and Russia ...and incidentally the US) may have (the Chinese are working on their own stealthy fighter, the JXX).
Thus, this thing is not a Raptor. But if it is better than the SU-35 already flying out there, then it will be the best fighter bar the Raptor ...better than any F-15/16/18, better than the Eurocanards (Typhoon, Rafale, Gripen NG), better than the Chinese fighters (JF-17, and J-10), and yes, potentially better than the F-35 (although that is a huge area open to contention)