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#11
PC Emulators are completely different to console based emulators
As others have mentioned, depending on the console being emulated, they all need different emulators. There aren't any 'one emulates all'
As also mentioned, there are no current ps3/360 emulators due to the 'as yet' unavailable power needed.
As with emulator, ymmv.
The Emulator Zone - Your Source for Emulation! is the site I use to get my emulators (they are good imo). I believe the one at the top of the list for each console is the highest rated. There are emulators for every console besides PS3 and Xbox 360 as mentioned already. For the games you must get, in most cases, ROMs. Just Google the name of the system and then ROMs. For example; gba roms. Good luck.
Nintendo - JNes
SNES - Snes9x 1.5x (don't remember)
SEGA Genesis - KFusion
Game Boy Advance - Visual Boy Advance
Nintendo 64 - Project64
PS1 - ePSXe
This is a good source for Emulators/ROMs/ISOs :)
Emuparadise.org - N64 Playstation Dreamcast SNES Genesis NES MAME ROMs ISOs