If you're limiting yourself to using analog cables, then this is probably your best bet. The included S-Video cable will work with the N64 and GC (also SNES), and the device itself will work with any older systems (pre-HD).
https://www.retrotink.com/product-page/2x-mini
Second-best would be one of those Pound or Hyperkin HDMI adapters. They're cheaper ($30), but you'll likely get a blurrier and darker image, as well as some slight lag.