cogadh: Absolutely wrong, emulators are not illegal.
keeveek: Yes they are. Most of them are using modified console BIOS which is copyright violation. You think how they are emulating the console? Using it's modified engine. Which is a violation. (I am 100% sure PSX and PS2 emulators use SONY's BIOS for emulation, don't know exactly how things are for nintendo)
Using an emulator when you actually paid for a game AND console? maybe not illegal, dunno.
No, pirating a BIOS is illegal. Emulators are not, however some emulators require a pirated BIOS to work. It doesn't make the emulator illegal.
You're right about Playstation emulators requiring a BIOS. This BIOS isn't distributed with the emulator in the same way that ROMs aren't.
VisualboyAdvance mostly runs fine without the GBA BIOS because few games actually used it in any way. There is an option to load the BIOS, as AFAIK there were a couple of games that wanted it.