Max speed of the aircraft is only one of the important variables in its performance. To the best of my knowledge, assuming all things including pilots skills being equal, factors that influence capability of a fighter are:
Rate of climb, maximum speed especially at low level, operational ceiling, endurance & range, turning circle, acceleration, sustained speed during turn. Last but not the least being radar & avionics. One can add weapon carrying capacity to the above for multirole fighter bombers.
On this basis, thrust to weight ratio, which has direct influence on acceleration, rate of turn & rate of climb as well as maximum speed, is of critical importance. Additionally, wing & fuselage design such as design of tail or canards, wing loading would also have major effect in a dog fight.
Generally a low wing loading (loaded weight divided by wing area) implies better manoeuvrability. Nearly all modern fighters are unstable which make these more manoeuvrable. Thrust vectoring is also primarily meant to make aircraft turn sharply without loss of speed. In 4+ generation and later aircrafts, ability to engage multiple targets and to shoot before you can be seen is considered the key factor. Since most dog fights are trans-sonic speed, maximum speed has become less critical.
In my humble opinion, Block-3 thunder with improved avionics & radar and equipped with 2 BVR and 2 WVR missiles would be a match for any aircraft except the ones with stealth technology. Would I like to see max speed of Thunder to be Mach 2 or better? Yes but not at the expense of any of the other factors noted above.