@SuperMew98
The Wii can play
GBA via emulation, that has tons of RPGs,
The Golden Sun games
Shining Force (not just updated graphics either, there is lots of extra game play added),
Final Fantasy 1 & 2 (extra's including a new story line and a couple of extra dungeons, as well as the updated graphics)
SNES both via VC and Emulation, list a few for that system
Megadrive/Genesis via both Emulation & VC, listed a few for that system
PSX is emulated but I never did check it out, Suikoden 1 & 2 might be ok on the Wii though, they are well worth playing
GB and GBC are also playable, there are a couple of good games on those systems but not that many
SMS and NES are emulated and via VC
Can't say I use my Wii that often though well not at the moment at least, but as far as emulation goes I only used it mostly for lightgun games
Xbox can be soft modded easy enough, the best system to emulate other consoles on, best to give it a bigger HDD
Dreamcast does not need to be modded, just a great console to start will, has limited support for emulation
PSP can be soft modded easy enough, supports PSX and is great for 16bit and under emulation
Wii can be soft modded easy enough as you will know, already outlined what it can play
PS2 can be soft modded easy enough, runs patched PS2 DVD's with no swap trick and has limited emulation support (more limited than the Dreamcast)
Saturn.. a swap trick works fine, but it is hard to explain how it works, this is only for playing saturn games realy
DS systems can play both GBA and DS via a flash kit for both slot 1 and slot 2, there are also some perfect 8 bit emulators for DS including NES GB/GBC SMS and GameGear, 16 bit emulators are ok aswell Genesis and SNES but some games do have issues and the screen is not big enough to handle SNES or Genesis correctly
DSi & 3DS (they don't have a GBA slot) can play DS games via a flash kit, the more powerful kits can play GBA as well via emulation & beter SNES emulation, all DS emulation also works on those (you can't play DSi or 3DS games via a flash kit though)