To assume J-20 is 4 tons lighter than Raptor without reason would be a stretch, but now, there is word from AVIC, the makers of the J-20, that that is the case. I'm not saying the reliability is indisputable, but that coupled with the many posts here that discuss how weight could have been saved (possible 3 ton loss on improved titanium alone, weight loss through DSI, omission of thrust vectoring, etc...) certainly makes the case for the possibility. Don't forget, the J-20 was designed specifically to be able to cope with inferior engines if needed. At this point, from what I can see, the only argument for why the J-20 could not possibly be that light goes along the lines of, "But USA couldn't make it that light 20 years ago! How could anybody do better than a 20-year old American design?" Well, that's called denial, not reasoning LOL Times are changing, and they change faster in China than anywhere else. Call it "extraterrestrial" if you want, but to many, the entirety of China's meteoric rise has seemed quite out-of-this-world.
I'm very glad you brought up the case of the F-15 having a superior TWR than the F-22 but under-performing when compared with the F-22. It shows that you realize that new, superior design can overcome TWR deficit. So how is it that you suddenly believe that there must be a "defiance of the laws of physics" for a 2016 J-20 with less thrust (though not necessarily lower TWR due to massive weight savings from cutting edge Chinese manufacturing techniques) to outperform a 2005 F-22 with more thrust? Seems entirely possible to me given your F-15 vs F-22 example, especially seeing as how the supercomputers used to calculate aerodynamics have had their capabilities evolve exponentially with time.
Now don't get me wrong. F-22's a lovely silver pony, still among the best in the world surely, but to assume that it's superior to a modern 5th gen delta canard made with cutting-edge manufacturing techniques and materials designed with the fastest supercomputers in the world all 20 years later in advancement... well, no need to finish that sentence, to be "kind" back to you.
Thank you for extending that kindness, I really don't need to make apologies for the Raptor, and as for "long lead" projects, the time and money spent on the Raptor were very well spent. There really is only one "Alien Bird!" and it continues to be the most powerful fighter aircraft on the planet, with the lowest RCS, the highest operating altitude, with 8 AAMs, and the highest supercruise of at least 1.6 to possibly 1.8 Mach....
So yes, it did in fact first flight in 1995, and achieved IOC in 2005, and yes there are "only" 183 operational aircraft extant in the world....but each one is very, very capable, as of tonight there are a dozen or so J-20's and not quite that many SU-57s...to that I would add that there are 200 F-35s flying and they are "rolling" off of a very efficient production line!
Taking the lead is always very expensive hard work,,, catching up is,, well its a goal to strive for!
We need not make nebulous claims,,, and the Raptor is a "Heavy Fighter",, the F-35 is a "slightly less Heavy Fighter", with a much great weapons bay volume than aspiring fifth gens,,,, so if those aircraft happen to be a little lighter, with less available thrust dry or in afterburner..
So yes, there is a great deal we do not know here on SDF,,, I did have an enjoyable afternoon conversation with an F-22 pilot this summer,,,, he got a real chuckle out of my "Alien Bird!" analogy! Heh! Heh! Hey!
I can promise you that USAF takes the J-20 very seriously indeed,,,, I can also promise you that PLAAF take the F-22 seriously as well! R-E-S-P-E-C-T is earned Bro, I do respect the J-20
