I'm a hopeless N64 fanboy and almost all my favorite games are on there, so I can't say very much about it objectively. I'd say it has the PS beat in graphics, but even I can admit it lost out in sound. It's also slim pickings for RPGs on the N64.
I found the DS line's build quality to be generally much lower than the Gameboy line. My GBA SP is still going strong after seven years of being dropped on the ground and generally mistreated, but my three-year-old DS Lite (that I treat with kid gloves) is already having shoulder button issues. The D-pad is extremely squishy and seems too small for the hole it sits in, making it very unsatisfying to use compared to the clicky goodness of the GBA. It also fails to read DS cards and GBA cartridges fairly often in my experience.
The original Xbox was pretty good. It had some strong exclusives like Halo and Halo 2, as well as JSRF. Xbox also tended to have better ports for multi-platform releases IIRC. Barring modded consoles, it was stupid to have to have the remote to play DVDs on the damn thing. Game demos included on DVDs were always cool though, I remember the Battlefront II demo being the only redeeming quality of Revenge of the Sith.
I have a Gamecube, but I only have three games for it so I can't really judge it. Not having any internal memory is a pretty glaring flaw for a sixth-generation console, but it keeps working if you gently nudge it (unlike the N64, which locks up if you give it a mean look). I like that I can reuse my N64's AV cables. I also like how the controller buttons are all very large, it makes it very satisfying to push them.