Get an original Xbox super cheap, Megadrive/SNES/NES/Mastersystem, all manner of handhelds, N64 (sort of) and Playstation (quite well) as well as loads of others. I'm sure it'll be better to play on than the Wii.
I can get one for under £20 but the Wii's been fine for me really, it does the job for emulating old games. I just can't decide whether or not I'll miss playing them on the original hardware. :/