I really enjoy making NES games.
They are the right mix of low level challenge, but also simple due to the hardware's limitations.
I've tried doing retro-dev for other systems, but none of them have ever stuck.
The GameBoy was my favorite system growing up, but I've found I don't really enjoy the mess that is z80 asm.
I love working with m68k, but have struggled with making Sega Genesis games because it feels like the quality bar should be so much higher.
I end up using a mix of modern tools like cc65,
Aseprite, VSCode, and Python.
Original NES games were almost written almost exclusively in assembly, but it's nice to have flexibility.
I write most of high level parts of my NES games in C, and just do the "fun" parts in assembly. ;)