Mig-21 vs EE Lightning
Mig-21 can turn tighter than Lightning, so in a turning fight the "bleed-off" won't matter, as Lightning won't last long enough to make Mig-21's turn rate deteriorate. In a straight-line fight, Lightning accelerates far faster than Mig-21 and has a better rate of climb, so it can engage/disengage at will... until it runs out of fuel.If Lightning initiates, expect 1 or two passes then it runs for home, with Mig-21 probably dying.If Mig-21 initiates, Lightning probably dies before it can accelerate out of danger. Mig-21 probably attacks out of a dive.Interesting "dogfight"... two aircraft primarily designed as bomber-interceptors trying to fight each other.
Mig-21 vs SAAB J35D
In the early years the (older) Draken was the better fighter. Why? Because of its radar, fire control system, weapons and the connection to the swedish air control system. The Draken was aerodynamically the best fighter of its time. The B-Draken was able to attack from the front earlier than the MiG-21.
The F-Draken had a very sophisticated Pulse-Doppler-Radar from Ericsson and a very good fire control system. They fired radar-guided RB27 an heat seeking RB28 missiles, which were improved versions of the AIM-26B and AIM-4D Falcon from Hughes. The (modified) danish Draken were superb attack planes, too.
That all said, the MiG-21 was an important plane for the East Block member states, built in high numbers. So it overtook the Draken due many modernization programs.
Mig-21 vs Mirage IIIe
The MiG-21 is more agile (superior power to weight) but in combat between the two it often came off worse because the Mirage III were piloted by better trained Israeli pilots with better (untypical of Mirage) AAMs. The Mirage had a generally better main radar but both are subject to upgrade in the modern world.
Overall I'd give the fight to to the MiG all factors being equal. Which they never are.
Mirage IIIE vs F8 Crusader
In exercises with our RAAF manned Mirages, USN Crusaders were generally at best the equal of the Mirage, but usually a bit sluggish and certainly not superior in maneuverability except at certain specific altitudes. F-8 were not well equipped with missiles until fitted with Matras, which our Mirages carried as standard. Later the later marks of Crusader were altered to carry a range of different missiles which overtook the performance of our own missiles. Later marks of the crusader were superior to the Mirage, and on board radars and other sensors were always superior