If you want your SNES emulation to be accurate, this won't cut it I'm afraid.

http://arstechnica.com/gaming/2011/08/accuracy-takes-power-o...

But if you're just doing run-of-the-mill SNES emulation, it should be great.

The raspi does have analog video output, but it's composite. If you're an old school gaming purist you'd want something with analog RGB output.