Would depend on who you asked and what parameters you seek.

Would you look at performance stats? There are two ways to look at that; overall, and for the inital operational generation(Time-frame.)

Combat record? On the surface Russian jets(according to "offical" western and some mid-east records) have poor records.

However; if one looked at all sources.

The 21 aquitted itself well as most jet kills in 'nam were MiG-17's (likely some Sino-produced equivalent as well.) It was employed to good effect during the Indio-Pak wars. And most Israeli kills were scored on jets sitting on the ground. A fact glossed over, yet, if one reads close enough revealed, it the publications of some "experts."

And as far as the gun-site and other evidence? In some cases one would not require a lope to see it's the same plane shot from different angles, or substandard collage work.

The MiG-25 has scored two exceptional kills (based on circumstance surrounding.) One finally confirmed, one questionable(Fact, IMHO.)

The Ethiopian conflict pitted Su-27 against MiG-29, in an even-handed match as can be found. The Su-27 came out on top of that.

The MiG-31(along with its cousin the 25,) has made some successful intercepts including SR-71's.

As well one can in most cases, Russian aircraft were either, killed on the tarmac, out numbered, out dated, flown by inadequately trained persons, did not have any support(AWACS, ect,) and many models were controlled(in a sense) by an outmoded GCI system.

My votes: MiG-15,21,25,31. Su-24,27. Tu-128/28P.

This is not criticize the Israeli tactics, as they show some true brilliance.

As well the training of US and Israeli Pilots.
For a time (at least 38 years) both countries have trained theirs parallel to pro-boxers, with sound fundamentals from the book, but allowing for creative thinking and devloping sublime "tricks" as well.

Whereas: Russia and many other nations did and some still do, train(ed) purely academic.

About soviet/russian made aircraft losses : "As well one can in most cases, Russian aircraft were either, killed on the tarmac, out numbered, out dated, flown by inadequately trained persons, did not have any support(AWACS, ect,) and many models were controlled(in a sense) by an outmoded GCI system." -- I agree.

The person is/was a military linguist, and he spent 20 years in the USAF. While that is not a "bad" thing. In fact it shows a degree of dedication, an honorable trait for sure. It would cast some doubt as to objectivity (both his own, and of his sources.)

Needless to say most analysts, Bill Gunston for exa. Report that the state of the Russian airfleet, Pilots, Ground Crew, and other support functions, is steadly improving.

"Combat record? On the surface Russian jets(according to "offical" western and some mid-east records) have poor records."
CAn you name one engagement in chich a mig-29 has shot down an enemy aircraft. I think MIg-29 shooting down its wingman's mig-23 is its only kill.