The Mig-25 gets far too little love.
To compare it to the Blackbird is to make perhaps an unfair comparison. The Oxcarts are an aircraft built to do one thing and do that thing to detriment of everything else. It flew over a target at maximum velocity, grabbed the data and got home safely. The YF-12 could shoot missiles. It also took a full day to get it ready to fly - something less than ideal for an interceptor. They required special fuel. A special starting fluid that ignited hypergolically. A specialised hanger. A specialised tanker force. A specialised engine. They were the product of the best engineers given the best materials, the best pilots and what amounted to a blank chequebook.
An awesome machine in their own right that was perfect for its mission.
The Mig-25 "Foxbat" was a very different machine.
It could do Mach 3 aswell. Once. It did it by making the engines an expendable part. Not really a problem when they're cheap to build. The R-15 turbojets had originally been designed for a single-use trisonic missile - and were updated to have a longer service life in an aircraft. Due to it's speed and engine design, it still holds the absolute air-breathing altitude record, and altitude with payload record. It also swallows 20 litres of kerosene every operating second at full throttle.
Titanium was expensive to work with and demanded a budget far beyond what was available for an interceptor that had to be produced in the hundreds, so it was instead built from Nickel Steel. Which meant it could be welded together using the same machinery and hardware as your average car, truck or washing machine. It allowed a high quality production to be achieved at minimal cost.
They matched a pair of massive engines and a steel airframe, to the most powerful radar possible to blast through ECM, and four of the largest missiles ever fitted to an aircraft. Or, dpending on version, ELINT hardware or reconnaissance cameras.
It operated from open airfields Siberia and Syria. In Libya, some rebels got a Mig-25 flying and uses AA missiles to shoot at ground targets. Syria is still able to get theirs flying every now and then. Saddam buried his before the last Gulf War, expecting them to survive the US attacks and be reactivated afterwards if his regime survived. They were almost effective in the first war, considering the gulf in pilot skill and the age of the airframes at the time.
The Foxbat has never really had the luxury of having well trained pilots at the helm, when matched against western hardware. Most were sold to tinpots keen to have The Fastest, or thumb their nose at the West. When employed by pilots who were gl;orified war thunder players, they made for Eagle and Phantom food. Just think of all the WT players turnfighting Zeroes and Spirfires in Thunderbolts.....
When given to a skillful Pilot who could use the aircraft's speed properly, they could achieve some remarkable results. An Iraqi pilot (Mohammad Rayyan) actually became an Ace while flying one - hunting Iranian Phantoms before getting himself downed by Tomcats. Another Iraqi pilot used the aircraft's speed to destroy an F-18 near Baghad during the first Gulf War. On another mission, a Mig-25 evaded a pair of F-15s to engage the F-111 Raven the F-15's had been escorting, forcing it to return to base. It then outran the F-15s to escape.
By the 90's they are completely outclassed, but still capable of engaging and being a threat. The reconnaissance variant however, became notorious
In the 70's, "Egypt" was flying them over the Sinai and just leaving the Isreali air force for dust. One was famously tracked at Mach 3.2, climbing and accelerating away from Isreali F-4s. Its engines needed to be overhauled, but they are a consumeable part.
India used them to fly over Pakistan at 65-70k ft where Pakistan's air defenses couldn't even detect it, let alone do anything about it. The first warning was the sonic boom in Islamabad. And, unlike the Blackbird, the Indian Migs were the Mig-25 RB. They could carry bombs. The Blackbird was known for it's ability to fly with impunity, rattling the windows of presidential palaces. The Mig-25 could do that - then drop a bomb or two for good measure. Where the Blacbird said "I'm up here and you can't do anything about it" the Mig warned "I'm up here and you can't do anything about it - and I also carry bombs."
That really annoyed Pakistan for some reason.
It's a bit like the difference between a Ferrari and a Dodge. Everyone lusts after the Ferrari, but there's something cheeky about the big friendly Dodge that's almost as fast, and a hell of a lot simpler and cheaper. It's a big lump of steel with massive engines and a thirst for fuel to beat the band - I'd have thought it'd fit right in in the US.
Anyway. The Engineers at Tumansky figured out how to modify the R-15 to sustain Mach-3 speeds. The Foxbat airframe was up to it. In the end, they didn't bother as the successor was on the way, with a very different mission. The Engineers at Lockheed considered fitting bombs to the SR-71 (Bomb anywhere in the world in 3 hours??) but for some reason - probably funding or because it would demand an opponent from the Soviets- decided not to.
Probably too much of a one-trick pony for DCS. But what a trick