Shitty top ten lists seem to be the chief export of crap magazines these days.
If you like reading horrible horrible stuff, read 1Ups "Worst Pack-ins" thing. My word its
horrible.
Did you know that Super Mario Land (GB) was shit? Yeah, I didn't either.
Back to this topic, I don't think there are 10 underrated consoles. Gaming isn't that old and diverse yet. And then, as others have pointed out, if your console is one of the most popular of all time, like the 2600 is, and the NES2 (since its just a NES) it obviously isn't underrated. That's just stupid. The C64 isn't a console, obviously, and even if it were it was HUGELY popular. The single best selling computer by a gigantic massive margin. In Europe they even got Street Fighter II for f*cks sake, which must have been 15 years or so after the machines debut. Its not exactly the red redheaded stepchild....
Underrated machines, that is, machines that were less popular in the mainstream than they would have been if people were paying attention, would be stuff like:
TG-16: I specify the US name here because the PCE market did well enough. The public didn't buy it, so the software lost was small, so the public still didn't buy it, so the software releases got even more sparse; the downward spiral.
Saturn (US): pretty much the same situation. Japanese Saturn owners got their socks knocked off, but the US game selection was pretty damn sad. See TG-16's downward spiral.
Gamecube: it has some*great* stuff and anyone who tells you otherwise either hates games or is trying to sell you something. Sadly the library of great games is really small, and during its day it really couldn't survive as someone's "only" system when the DC and PS2 were around with much larger libraries.
Dreamcast: one of the best libraries ever, and most of it came out in two years. What would it have been like if Sega hadn't been forced to abandon it to move to Xbox and PS2? We'll never know.
Colecovision: this is so much less popular in the pre-crash scene than the 2600. I can't figure it out since it was pretty great and the 2600 is, honestly, not very good. At all. %90 of 2600 games are unplayable for me, and the arcade conversions are really great on Coleco instead of terrible crap. I was an active little gamer dude back in the days of the 2600, but I spent my cash at the arcade and on the Colecovision.
As far as I'm concerned that's pretty much it. Stuff like the 3D0, CDi and Jag did poorly for a reason; they are garbage. The fact that even a single person owns and operates a collection for these systems means they are overrated if anything. The SMS wasn't that popular, but compared to the NES, it wasn't that great. I own a pretty decent SMS collection and I barely even touch it. I think it probably gets about the level of respect it deserves. Its...equirated?
If handhelds are included I'd say that the Japanese underrated the Wonderswan, and the whole world underrated the Neo Geo Pocket.