I do not think the SU-35 has a chance against a head-on encounter with the F-35 because by the advertiser's statement, the IRBIS-E can only detect target of RCS 0.01 m2 at 90 km. With that detection range, Su-35 will detect F-35 (RCS of about 0.001 m2) at around 50-60 km which is too late already.
I believe the detection range of the IRBIS-E will make it on par or even better with the rest of the Europe & U.S 4th generation fighters but not good enough for F-35, F-22; hence a development of PAK-FA is necesarily.
Actually, a lot of thought has lately gone into looking a possible answer to the threat of the F35 in a regional antagonistic environment.
More than that, the F35 was considered to be armed with Meteor missiles instead of Amraams, which are superior in range at least.
Right now the Su35 was the only plane that would come out on top in most scenarios.
These consider the relative size of fleet / price paid per unit, i.e. for the same money you get a lot more Su35s
Kinematicaly the Su35 is superior with superior range, and loiter time,
It is true there is some doubt as to whether the Su35 will be able to pick the F35 at a reasonable range, there are indications that it may as there are indications that it may not,
The Su35 however has the ability to outfly Amraams and Meteors, whilst at the same time identifying the launch vector of the incoming missile and training it's IRST sensor to it for targeting,
it then carries more missiles and has more diverse payload to engage the F35 with a combination of IR and EM BVR missiles.
The explanations given by the russians on the plane provided a sense of real understanding of the dangers and abilities of a Stealth adversary and how one could go about dealing with it.
Remember it is not necessary to eliminate the threat of a stealth plane, it is enough to simply make it costly for it to operate over the area.