For the uninitiated: 5th generation fighters are the most advanced aircrafts, designed to incorporate numerous technological advancements, including all-aspect stealth even when armed, Low Probability of Intercept Radar (LPIR), high-performance air frames, advanced avionics features, and highly integrated computer systems capable of networking with other elements within the theater of war in order to achieve an advantage in situational awareness.
So far, there has been only one 5th generation fighter in service: USAF's Lockheed Martin F-22 Raptor. Its stealth, speed, agility, precision and situational awareness, combined with air-to-air and air-to-ground combat capabilities renders it the most lethal fighter in the sky right now. Each of these cost $150 million, and there is a ban on its export (even to its closest allies).
Unfortunately, it has been killed, and replaced by the F-35 Lightning II. The replacement low capacity multi-role fighter is single-engined and designed to be America's "premier surface-to-air missile killer and is uniquely equipped for this mission with cutting edge processing power, synthetic aperture radar integration techniques, and advanced target recognition." It will have 3 variants - one for the USAF, one with STOVL capability and one carrier version. But it's also less maneuverable than air superiority fighters 50 years old, has no super-cruise capability, can carry only 2 A2A missiles in its internal bay, and costs $130 million each. This will be NATO's primary fighter in the coming decades.
Now, the Russians have crashed the party with the Sukhoi PAK FA T50. Still in the prototype stage with the airframe and new NPO Saturn engines being tested out, the T50 is the only aircraft that can possibly match the F-22. With an unusual canard configuration, fully movable V-Tails, vertical S-shaped intakes leading to exhausts placed far apart (increasing coupling effect) and 3D thrust vectoring, it's much more agile than the F-22, albeit with a higher RCS. Also it's being fitted with IRST optical/IR search and tracking system, which the F-22 lacks. It won't be in production till 2015, and will cost an estimated $100 million each. Will be sold to India and other various countries, like Vietnam.
Finally, here's China's answer. Back on 11th January, they revealed their 5th generation fighter: the Chengdu J-20 Black Eagle. Admittedly, it will have nothing compared to the F-22's speed, agility or stealth (though probably will be comparable to the F-35 and F-18 variants). But it is a large aircraft with a greater weapon payload and increased range, and will probably fulfill the role of a super sonic long range interceptor, strike fighter, reconnaissance aircraft, electronic attack platform etc. If the Chinese can actually procure it, USA will have to rethink its entire military strategy of a possible strike against China.
We really need an all out war right now to see who wins!
But apparently, as that's too much to ask for, I ask you: hypothetically, if all these projects are completed without a hitch, which region d'ya think will end up having the upper hand in ariel combat?
EDIT: Since it's not apparent to everyone, when I was asking for an all out war, I was being sarcastic.
So far, there has been only one 5th generation fighter in service: USAF's Lockheed Martin F-22 Raptor. Its stealth, speed, agility, precision and situational awareness, combined with air-to-air and air-to-ground combat capabilities renders it the most lethal fighter in the sky right now. Each of these cost $150 million, and there is a ban on its export (even to its closest allies).

Unfortunately, it has been killed, and replaced by the F-35 Lightning II. The replacement low capacity multi-role fighter is single-engined and designed to be America's "premier surface-to-air missile killer and is uniquely equipped for this mission with cutting edge processing power, synthetic aperture radar integration techniques, and advanced target recognition." It will have 3 variants - one for the USAF, one with STOVL capability and one carrier version. But it's also less maneuverable than air superiority fighters 50 years old, has no super-cruise capability, can carry only 2 A2A missiles in its internal bay, and costs $130 million each. This will be NATO's primary fighter in the coming decades.

Now, the Russians have crashed the party with the Sukhoi PAK FA T50. Still in the prototype stage with the airframe and new NPO Saturn engines being tested out, the T50 is the only aircraft that can possibly match the F-22. With an unusual canard configuration, fully movable V-Tails, vertical S-shaped intakes leading to exhausts placed far apart (increasing coupling effect) and 3D thrust vectoring, it's much more agile than the F-22, albeit with a higher RCS. Also it's being fitted with IRST optical/IR search and tracking system, which the F-22 lacks. It won't be in production till 2015, and will cost an estimated $100 million each. Will be sold to India and other various countries, like Vietnam.

Finally, here's China's answer. Back on 11th January, they revealed their 5th generation fighter: the Chengdu J-20 Black Eagle. Admittedly, it will have nothing compared to the F-22's speed, agility or stealth (though probably will be comparable to the F-35 and F-18 variants). But it is a large aircraft with a greater weapon payload and increased range, and will probably fulfill the role of a super sonic long range interceptor, strike fighter, reconnaissance aircraft, electronic attack platform etc. If the Chinese can actually procure it, USA will have to rethink its entire military strategy of a possible strike against China.

We really need an all out war right now to see who wins!
But apparently, as that's too much to ask for, I ask you: hypothetically, if all these projects are completed without a hitch, which region d'ya think will end up having the upper hand in ariel combat?
EDIT: Since it's not apparent to everyone, when I was asking for an all out war, I was being sarcastic.