Crits

Not sure about the extras situation on most of these, so check DVDcompare if you want. Safe to assume the Criterion editions have exclusive ones but most of these will probably have substantial extras on their own
Anatomy of a Murder (Sony 4K, mono is only a 5.1 downmix unfortunately)
Army of Shadows (Studiocanal is releasing a 4K - seems the color grading is debated)
Boyhood (Arrow has a 4K)
Breaking The Waves (Curzon 4K)
Crash (has a 4K from Arrow and just a blu from Criterion, Arrow has more extras but Criterion has a few different ones)
Dekalog (Arrow is in the original 25fps, split onto more discs for better encode)
Diabolique (theres an OOP 4K restoration on blu, worth holding out for a 4K disc perhaps)
Don't Look Now 4K (Studiocanal's version has an FIM encode)
Dr Strangelove (Sony has a 4K)
Dressed to Kill (Kino 4K, only caveat is the subtitles are BLINDING on an OLED, so if you don't have a player with subtitle brightness options and you rely on them then it's worth knowing)
Easy Rider (Sony has a 4K in the UK)
Election (getting a Paramount 4K, they're hit or miss so wait for reviews)
Ghost Dog (Studiocanal 4K)
Godzillas and most Kurosawa discs have 4Ks in Japan (without English subs), will likely get upgrades soon, especially Seven Samurai since it's getting a theatrical rerelease in the US)
His Girl Friday (Sony 4K)
In the Heat of the Night (German 4K has DV / HDR, Kino's 4K is only SDR)
In the Mood for Love (Criterion's own blu-ray (not included in the 4K) has the original color timing, the 4K is revisionist if you dislike it)
Infernal Affairs Trilogy (has Hong Kong and French 4Ks, Hong Kong discs have english subs but might be worse translation)
Inland Empire (older blus or DVDs - some might not like the AI upscale on the Criterion but the extras are way more substantial on the Crit)
Inside Llewyn Davis (Studiocanal is preparing a 4K of this, might be worth holding off)
Jackie Chan Emergence of a Superstar (88 Films individuals likely has better encodes, will be more expensive)
Last Emperor 4K (Arrow better encode)
Last Picture Show 4K (not a full recommendation as apparently it has worse encoding, but the Sony 4K in the Columbia Classics 3 boxset has the theatrical cut if you want that, might also be pretty cheap on eBay now that the Criterion is out)
Last Temptation of Christ supposedly has a 4K restoration - blu-ray is pretty dated so it might be worth waiting for
Long Good Friday 4K (Arrow has most of the same extras minus a documentary about handmade films, likely better encode)
Memories of Murder (Curzon just released a 4K)
Merry Christmas, Mr Lawrence (Arrow blu is in correct aspect ratio - a newer 4K restoration has been done, just not on any disc yet)
Miller's Crossing (The Fox blu-ray is the original cut of the film, Criterion was told to cut a bit by the Coens)
My Own Private Idaho (German disc has better encode)
Naked (BFI has newer 4K transfer on blu, different aspect ratio)
Naked Lunch (Arrow has a 4K)
Paris, Texas (Studiocanal and Curzon have 4K remastered blu-rays - all will likely release actual 4Ks eventually since this year is an anniversary and I think they're bringing it back to theaters)
Peeping Tom 4K (Studiocanal has better encode, most of the same extras)
Punch-Drunk Love (Sony has a 4K of this but it's locked to a boxset)
Ranown Westerns have a bunch of different extras on the Indicators and will be pretty cheap when they do their 3 for 15 sale, seems like the 4Ks are overall better if you don't care about extras though
Scanners (Second Sight has different extras and more natural color timing if you prefer that - due for a 4K anyway)
The Game (Arrow has a slightly better encode, less extras, and an alternate 480p 1.33 version - they also released an edition with a massive book and most of the Criterion extras on a DVD copy)
The Great Escape (Kino has a 4K)
The Killing & Killers Kiss (4Ks from Kino)
The Parallax View (the audio on the Criterion removes all the bass - supposedly the Imprint has better audio, worth looking into before buying)
The Trial 4K (Studiocanal has Dolby Vision)
The Vanishing (Studiocanal blu-ray has a newer 4K restoration)
Thief Blu-ray (Arrow has a slightly better encode, most of the same extras, and if you get the original limited edition 2 disc set it includes the original color timing / theatrical cut)
Three Colors 4K (Curzon better encode)
Time Bandits 4K (Arrow has has a better encode)
Tokyo Story has a 4K restoration recently completed, will get a 4K eventually

Twin Peaks: Fire Walk With Me is likely to get a 4K stateside soon as Janus has been teasing it online, and there's a French SDR 4K coming soon
Vampyr (Eureka's blu is a more cleaned up restoration)
Walkabout 4K (Second Sight has a blu-ray without the encode/color issues and it's from the same transfer - they will likely do a 4K)
Wings of Desire (Curzon 4K better encode)