I've developed an interest in titles from the '80s and '90s that have nearly-identical or perfect reproduction of game logic across platforms that don't seem particularly compatible. Porting from 6502 or Z80 is not something that we can expect to be automatic, so when we see something like this in an age of ISA-specific assembly, it's a little more impressive as it implies either really great standards in game logic description, the use of (then-less-popular) high level languages, or a mix thereof.
Examples:
-Balloon Kid on GB/GBC vs Hello Kitty World on Famicom
-Sonic Spinball on Genesis ported to Game Boy Advance (this is confirmed written in C)
-Super Mario All-Stars on SNES; obvious re-toolings of original NES code (easy 6502 --> 65c816 here)
-Pac-Man on Z80 arcade to Neo-Geo Pocket Color (the most accurate contemporary non-emulated home port I've found; even has the "turn-on-stop" bug reproduced). This one is a head-scratcher given the largely unrelated architectures at work.
-Earthworm Jim on Genesis --> PSX, Saturn (gameplay is spot-on, as are animation sequence timings... implies good use of established and agreed data structures at least)
-Sonic CD to Windows 95 (not sure exactly what's going on here, but the logic and drawing looks 1:1 reproduced)
-Metal Slug on Sega Saturn
-Fantasy Zone II DX on Sega System 16C, brought to Nintendo 3DS (M2 confirmed game logic was done mostly in C)
Non-examples, where enough differences imply a careful rewrite but not a port:
-Pac-Man 2 on SNES / Genesis
-Jim Powers on SNES / Genesis
-TMNT: TiT on SNES / TMNT Hyperstone Heist on Genesis (despite different stage data, the engine for the turtles and enemies is also identifiably different, with differences going beyond the lack of Mode 7 scaling screen toss)
-Sonic & Knuckles collection for PC (Hacky emulator that hooks sound cues and played WAV files and MIDIs, not a port). This applies to the Sega Smash Pack PC games as well.
Examples:
-Balloon Kid on GB/GBC vs Hello Kitty World on Famicom
-Sonic Spinball on Genesis ported to Game Boy Advance (this is confirmed written in C)
-Super Mario All-Stars on SNES; obvious re-toolings of original NES code (easy 6502 --> 65c816 here)
-Pac-Man on Z80 arcade to Neo-Geo Pocket Color (the most accurate contemporary non-emulated home port I've found; even has the "turn-on-stop" bug reproduced). This one is a head-scratcher given the largely unrelated architectures at work.
-Earthworm Jim on Genesis --> PSX, Saturn (gameplay is spot-on, as are animation sequence timings... implies good use of established and agreed data structures at least)
-Sonic CD to Windows 95 (not sure exactly what's going on here, but the logic and drawing looks 1:1 reproduced)
-Metal Slug on Sega Saturn
-Fantasy Zone II DX on Sega System 16C, brought to Nintendo 3DS (M2 confirmed game logic was done mostly in C)
Non-examples, where enough differences imply a careful rewrite but not a port:
-Pac-Man 2 on SNES / Genesis
-Jim Powers on SNES / Genesis
-TMNT: TiT on SNES / TMNT Hyperstone Heist on Genesis (despite different stage data, the engine for the turtles and enemies is also identifiably different, with differences going beyond the lack of Mode 7 scaling screen toss)
-Sonic & Knuckles collection for PC (Hacky emulator that hooks sound cues and played WAV files and MIDIs, not a port). This applies to the Sega Smash Pack PC games as well.