The real issues with the F-35 are due to bureaucracy and procurement, rather than the actual aircraft.
Not only that, the other aircraft you're talking about - the J-20 and Pak-FA are either crappy or do not exist. The F-35 has already made trials. It takes time to get something like this right.
Its not going smoothly, but it will be worth it in the end. America and her close allies will get a real 5th generation multi-role stealth fighter which will be usable for probably the next 30 years in any potential conflicts.
The J-20 is a joke, and its the only other stealth out there. Why is it a joke? Its about twice the size of the F-35, and it has rivets on the outside of the aircraft. RIVETS! Do you know how stealthy that design is? Its likely only slightly more stealthy than a newer F-15.
Back from the dead, I'm afraid.
