What band can you not beleive is more popular?

I mentioned those bands but it's relative. Compared to later Genesis, Rush and Pink Floyd I think they are all very under rated and under recognized outside of prog circles these days. I didn't mention King Crimson or Porcupine Tree partly because I think they have pretty big followings these days among younger folks and among music fans in general although not as much as PF and Rush. Out of those I did mention Camel does seem to have a bigger following among younger people these days at least partly because they are an acknowledged influence on Opeth.

Maybe in the past five to ten years or so HTM has been buried under the carpet but before that they were considered to be by many to be the best prog band in the US. They even headlined the second Nearfest in 2000. The Muffins are another band from the same era and location(DC/VA area) who are a bit overlooked these days. Personally I have more of a  hard time considering HTM to be underrated among prog fans though unless we are talking just younger prog fans.

5uu's, Airlord, Apogee, Blue Effect, Emmanuel Booz (especially for the Dans quel etat j'erre album), Alex Carpani Band, Carpe Nota, Cell15, Conqueror, Eccentric Orbit, ExCubus, Galleon, Gerard, Le Grand Sbam, Greenslade, Grobschnitt, Hamadryad, High Wheel, Horse Lords, The Hosemobile, Karakorum, Karcius, Kharmina Buranna, KingBathmat, Land of Chocolate, Little Atlas, Mangrove, The Mercury Tree, Mezquita, Mikromidas, Monarch Trail, Moon Letters, Morse Code, Mosaico, Nau Aletheia, Nexus (the Argentinian band), ni., Nil, Novalis, NoVox, Oblivion Sun, Othello Syndrome, Paatos, Pancake, Matthew Parmenter's solo stuff, Pentwater, Emme Phyzema, PoiL, Puppet Show, Qoph, Quantum Fantay, Rainbow Theatre, Ring Van Möbius, Scherzoo, Schnellertollermeier, Sebastian Hardie, Sezione Frenante, Simon Says, Social Tension, Solaris, Spaced Out, Spleen Arcana, Stratus Luna, Tale Cue, Talisma, Thinking Plague, Time Shift Accident, Trilogy, Triumvirat, Underground Railroad, Versus X, Voyag3r, Dan Weiss, White Willow, Wyxz, WytchCrypt, Zenit, Zombi, Zomby Woof

I know. Instead of listing all these bands, I should just write reviews that should at least convince somebody to listen to them. Why can't days be 48 hours instead of 24??

 There's not a whole lot of popping going on in my head (more like pooping). I dragged the laptop over to the CD shelves and just went through them alphabetically. Probably missed a couple dozen.