Since I mostly just play GBA and DS games nowadays, mGBA and MelonDS are my two go-to emulators. For other consoles, growing up in a poor household, emulation was my primary form of gaming so I went through quite a lot. This is mostly based off rough memory.
NES - Nestopia I believe was my main.
SNES - Being my favorite retro console, I've used a ton. ZSNES was my childhood emulator, and I still like it the most I think. It's rough and hard to navigate, but it's also just so...warm? The dated design and snow graphics are so nice and bring back fuzzy memories. For awhile, I used Snes9x, which is solid but...boring. In recent years, I've taken up Higan to honor its late creator.
N64 - 1964 was my main since as a kid, I thought you had to pay to use Project 64 I've barely play N64 games, despite being one of the few 'retro' (pre-PS2/Gamecube/Xbox by my standards) I actually physically grew up with (it, SNES and Atari Jaguar -- seriously), I don't have much fondness for the system, so I barely tried emulating it.
Gamecube - Dolphin, but my PC sucks so I've only been able to play a few games on it well.
Genesis/MegaDrive/S-CD - KEGA Fusion. Like ZSNES, I'm sure there are better emulators out there, and I've had a fair share of issues with KEGA, but it's also just really warm and fuzzy for me. Noooot sure if they exactly count, but I also had a ton of those SEGA Genesis compilation discs for PS2 growing up and played religiously.
GB/GBC/GBA - Aside from mGBA, I grew up on VBA. Still not particularly sure what mGBA does better than VBA and VBA had more quality of life improvements so I might honestly just go back.
DS - Aside from MelonDS, DeSmuME was my main growing up. Unlike VBA to mGBA however, DeSmuME is not great and I have no real desire to ever use it again. I've also used no$GBA a few times, mostly to bypass a gamebreaking bug that DeSmuME caused for Digimon World DS.
PSX - ePSXe. Could not figure out how to set this up til my mid teens, lol.
PS2 - PCSX2. To this day, the only game I could get running reasonably well on this thing was Persona 4, but then Persona 4 got a PC release so it became irrelevant for me once again, haha.
PSP - PPSSPP, though I tried (and failed) to use JavaPSP or whatever it was called a few times.
WonderSwan - Oswan.
Arcade - MAME, thought I've gotten a grand-total one one game running on it.
DOS - DOSbox