Like monocle said, Xenoblade on New 3DS. It wasn't a pretty game, but neither was the Wii version, and it ran perfectly well.

Virtua Fighter on Sega 32X is actually better than the Saturn version of the game, with simpler character models but none of the flickering or instability of the Saturn version.

Doom on the SNES and GBA. In the former case, Doom on SNES was somehow playable despite the SNES's wimpy hardware compared to the 5th gen consoles getting ports at the time, and even did a better job at recreating some of the original level layouts than most ports. The GBA version gets credit for coming  early in the system's life and being arguably the first solid handheld FPS.

Prince of Persia had a fairly good NES port.

Dante's Inferno on the PSP was a decent port of an HD game.

Ff15 to mobile devices was incredible.

The GBA CPU was much better than the SNES, Doom is very much a CPU driven game.

So impossible port? Nah.

Crysis 1 was running on the Console-optimised Crysis 2 engine. Otherwise it would have been one of those "impossible ports".

Well. Half Life 2 can run on fixed function PC GPU hardware (I.E. The very first Geforce GPU). That's a GPU or two generations before the original Xbox. So it's not entirely unsurprising.

And Doom 3's minimum PC requirements is a Geforce 3, so it fits in with the original Xbox.

Weren't their minimum RAM requirements far, far more than the mere 64MB Xbox had?

Google says Doom 3 wanted 384MB minimum and Half Life 2, 1GB.

Indeed. Need to keep in mind though that consoles weren't running a monolithic OS back then though.
These days the DRAM discrepancy is far far far less.

The Witcher 3 complete edition and shadow of war on the switch.

Those are great ports.

None. Most ports end up even below my low expectations. Though there are some first party games I was impressed with.

How about we not troll for no reason, ok?

hmmm.. some games that come to my mind are Doom 1 on Snes, Doom 3 on Xbox, Half Life 2 on Xbox, The Witcher 2 on x360, Rise of the Tomb Raider on x360, MGSV: The Phantom Pain on Ps3 and X360, MGS3 on 3DS, Xenoblade Chronicles on 3DS, Injustice on Ps Vita and some others that i dont remember now.