I'm really curious about what you consider to be the "best" emulator out there, as a Dolphin dev.
Please clarify your choice. I know it's really subjective, that's kinda the point

The other Wii emulator.
Ok ok, serious answer. Emulators face different challenges and have different goals. So it's really hard to gauge a "best" metric when all possible qualifiers are pretty flexible!
But if I had to pick one... without any hesitation, it's Higan. It has achieved cycle accuracy in the console itself, which is on its own an astonishing feat that almost no other emulators ever achieve, and has moved on to building that accuracy for obscure and rare cartridge chips for the Super Nintendo. And behind it all is an incredible preservationist effort unlike any seen in emulation before, literally involving getting and scanning the PCBs and cartridges of every single SNES title ever made! Byuu is doing such incredible work!
Also Higan isn't just a Super Nintendo emulator! That whole project is so incredible I'm in awe that Byuu has been able to achieve all of this. I know he's had a lot of help with donations and such, but still, it's SO MUCH!
If I were a dev, I would put my vote to that Switch emulator. Alas I am not, thus my vote will be lost into the void.
As much as I love Dolphin, for me it is PCSX2, as I was able to play Kingdom Hearts on my computer before Square started milking our wallets with the Kingdom Hearts remakes. Multiple times.
I always have been a Nintendo fanboy! So my preference goes toward any Nintendo system or emulator of course. Especially the classic systems such as the Gameboy, SNES and Nintendo 64. Sadly, Nintendo 64 emulators have been lacking compared to emulators such as Dolphin. Maybe we are just spoiled. You are usually better off using the Visual Console within Dolphin than using Project64, provided the Nintendo 64 game in question is available for the Virtual Console.
My favourite emulator is probably Intel's x86 emulator - it's been hit recently with a few bugs, but seems to have done pretty well generally since it's release in the pentium pro in '95
I don't know if you'd consider it an "emulator" or a "suite," but besides Dolphin, BizHawk is definitely the best. Tons of configuration options, tools, and incredible accuracy since it was built for TASing.
My vote goes to GBE+.
Totally unbiased opinion, I swear.
having recently discovered bgb, it helped me out loads with my GB Card reader project since its so accurate and its errors are direct and tell me exactly what is wrong