The F-15 Eagle has put up one of the best records of any air-superiority fighter – ever. It has scored over 100 air-to-air kills with no losses. Yet while the development of the Su-27/30/33/35 and J-11/15/16 families of the Flanker from Russia and China have closed the gap significantly, the Eagle remains very lethal – and keeps getting better.
Part of it is the inclusion of new sensor capabilities, like the Legion pod, that enable the F-15 to do thing the Su-27 can do. Another part has been upgrades to the existing systems, like the AN-APG-63 radar, which has been replaced by a new version with an active electronically-scanned antenna version known as the APG-63(V)3.
According to MilitaryFactory.com, the Air Force did give the entire F-15 fleet an upgrade known as the Eagle Passive/Active Warning and Survivability System, or EPAWSS, which gave the F-15C/D an improved chaff and flare dispenser, a digital radar-warning receiver, and a towed decoy. This gives the F-15 a better chance against enemy surface-to-air or air-to-air missiles.
But the F-15 from the get-go had a lot of advantages. It could carry up to eight air-to-air missiles (today, the load is usually four AIM-120 AMRAAM and four AIM-9X Sidewinders), and it had a 20mm M61 Gatling gun with 940 rounds of ammo. It has a top speed of 1,875 miles per hour, and an unrefueled range of 2,402 miles. Boeing has been pitching an Eagle 2040C that would add even more missiles to the F-15's already formidable armament.
Over 1,500 F-15s of all types have been built, and the production line is still open, producing variants of the F-15E Strike Eagle for orders by Qatar and Saudi Arabia. You can see a video about why the F-15 is aging so well below.