Staff Writer (Updated: 5/18/2016):
It should be noted that through most of the Cold War, the MiG-23 was thought to be nothing more than a "serviceable" and "highly utilitarian" aircraft at best. It was only some decades later that the old Western observations were upgraded to conclude that the MiG-23 was an impressive design in its own right, one that could match or (in some cases) out-best many of the available Western counterparts of the time.
About the MiG-27 "Flogger"
The MiG-27 "Flogger" is a direct development of the MiG-23 detailed in this entry and has its own write-up elsewhere on this website. The MiG-27 is essentially a dedicated ground-attack fighter-bomber form of the MiG-23 "Flogger" fighter / interceptor. It features the same swing-swing capability but is armored for low-level strike runs, has a broadened ground ordnance role across more external hardpoints and sports new fixed intake inlets. Its engine is decidedly less-complicated and features a simpler nozzle for the reduced-performance role. The twin-barrel cannon of the MiG-23 has given way to a multi-barrel type and special target acquisition systems are standard as is a terrain avoidance radar. The MiG-27 is discernable from the MiG-23 by its sleeker tapered nose cone assembly (promoting better "lookdown" capabilities). The MiG-27 was developed in two major derivatives under the NATO codenames of "Flogger-D" and the "Flogger-J". Use of the MiG-27 was primarily with the Soviet Union and India and began deliveries in 1975, ultimately seeing retirement with Russia in the 1990s. India took up license production of the type under the Hindustan Aeronautics banner as the Bahadur (or "Valiant").
Mikoyan-Gurevich began as a manufacturer of piston-powered fighters during World War 2 with their most notable creations being the "hotrod" MiG-1 and MiG-3 fighters. Success continued in the post-war world with the unveiling of their revolutionary single-seat, single-engine MiG-15 "Fagot" jet-powered fighter in the Korean War - coming as quite the surprise to NATO forces to which the North American F-86 Sabre was directly developed to counter the new threat. The MiG-15 was followed into service by the much-improved MiG-17 "Fresco", another single-seat, single-engine implement with greater handling and performance overall. The MiG-19 "Farmer" then appeared as a twin-engine solution with supersonic (Mach 1.0) capability. Mikoyan-Gurevich found additional success with the development of the MiG-21 "Fishbed" - a Mach 2-capable single-seat, single-engine fighter that went on to be used throughout the world as both an interceptor and a limited strike fighter. This lengthy history had cemented Mikoyan-Gurevich as a major player in the development of Cold War jet fighters and solidified valuable experience gained in the design and development of different wing systems to solve different speed criteria and furthered the firm's understanding of jet-powered machines to keep Soviet air forces on par with their American counterparts.
By this time, McDonnell Douglas had brought online the fabulous F-4 Phantom II, a twin-seat, twin-engine Mach 2-capable fighter with a strong dogfighting prowess and inherent strike capabilities. The F-4 featured a powerful radar system coupled with high performance specifications and quickly became the primary mount of the USAF, USN and the USMC during her reign and, later, was fielded across Europe as an ultimate Soviet deterrent. The F-111 Aardvark was another American Cold War fighter design intended to solve a need for both the USAF and USN in one fail swoop. It featured a twin-seat, side-by-side cockpit, powerful twin engines and variable geometry wings for different flight performances. However, this expensive design bloated to become a long-range strike aircraft and was far from a fighter in the end product. Regardless, the F-4 and the F-111 would be the MiG-23's principle adversaries during the latter's design and development stages.
The MiG-21 "Fishbed" was good for what it was initially designed for - speed. It could climb fast and achieve speeds of up to Mach 2 while fielding capable avionics and a weapons system that included both short-range cannon and longer-range missiles for most jobs at hand. However, if the MiG-21 was deficient in any areas it was in operational range, combat payload and its reliance on ground-based interception to help guide the system to a target area (no self-sustained sensors were onboard to handle such actions). Jet powerplants had always proven thirsty since the days of World War 2 and post-war jet technology the world over had yet to wholly solve the need for greater range output out of their engines - though progress was sure and steady by the time of the MIG-23 development. The clipped delta wings and slim fuselage of the MiG-21 had limited its armament potential across just four hardpoints by the time of the later production models. In all, this tailed-delta design was adequate for the interception role and, though it was developed into a ground strike variant, it was far from the answer of a the true multi-role performer that the Soviet Air Force was now looking for.