If anybody wants a good recommendation for Nintendo DS emulators, obviously DeSmuME is the logical choice, but I really can't help but recommend the x432r fork even if it won't get as many updates as the main emulator, because this fork lets you upscale the native resolution and apply Anti-Aliasing. If I recall correctly though, this is all done by the CPU, so you may not be able to just crank everything to max per se...
I mean, look at this! I'm stunned at how good some DS games can actually look when they're not rendered in a lower res than Doom!
Edit: Agh! How on earth did I forget to mention this!?
It's a Sega Genesis emulator that's focused on accuracy above all else. How much accuracy?
Last I checked, it requires a 2nd-gen i5 ~3GHz at minimum to run full speed (new versions may have eased this up though).
Debugging features seem to show a lot of promise too, but that's hardly my expertise.
It's also left open enough that it could adopt other emulation cores in the future, but you can read more about that on the website.
That "non-mess" link that Stiletto provided is really good one for this topic btw.
It links to MAME now because MAME and MESS were merged together back in May (I always wondered if they'd ever do that).
Kind of late but...
Gameboy emulators don't come better than BGB. Accuracy, compatibility, features (excellent debugger), all covered.
Sorry, fairly old post, I know, but I'm interested; do you know how this stacks up to Gambatte? That's been my emu of choice for some time, if not the VBA-M core in Retroarch that gives some nice screen filter options (but I wish there were more that emulated that green hue).
The fact that BGB supports linking Game Boys might give it a leg up over Gambatte, but I'm not super familiar with Gambatte's "under-the-hood" features...