I bit the bullet and purchased the ExtremeCap U3 capture device and the Wii to HDMI Converter. The ExtremeCap allows me to record 1080p HD video at 60 frames per second using 60 mbits per second. It's real-time too, so I can actually play games using the preview window, no noticeable lag. Meanwhile, the Wii to HDMI converter allows me to play GameCube and Wii games at 1080p resolution through HDMI, which I then capture with the ExtremeCap. This means: 1080p scaled GameCube games with no emulation.
I didn't think it would make all that much difference, but it really, really does! Just look at this comparison!
First, the old, compressed capture, using the best possible in-game lighting conditions and a relatively high bitrate. The result is a very compressed looking video at 720 × 480.
And then, the upscaled version recorded fully digitally. Even though the lighting is terrible by comparison, you can still see almost double the detail on the staff, in Fox's fur, and his wrist computer. You'll have to click the image to see the full resolution (1862 × 1011, cropped 1080p).
This is amazing, but I'm sure you're wondering, "Why now? What is he recording this for, and what's that little red bar in the Staff energy bar?" Excellent questions. I spent my entire evening testing out the ExtremeCap on my Star Fox Adventures Preview Disc, the disc they put in store kiosks. I will soon use this footage to make a video about the differences between the final game and the preview version. There are a lot of subtle changes, and a couple of mysteries solved. This is a video I've been wanting to do for years, and now it the perfect opportunity. Keep a lookout for it!