Journey to the Center of the Earth may very well be the first prog album I ever heard, and man did I ever love that album. I think I may have worn out my sister's copy of it. Rick Wakeman has a few other good albums as well, I was also quite fond of
The Myths and Legends of King Arthur and the Knights of the Round Table.
It is definitely more cerebral, and more technical.
Rock to me should be kids in a garage with grit and determination and, if enough talent, making it big without compromising with studio tricks and sappy love songs. I'm thinking of Styx after Dennis DeYoung took over. Luckily the rest of the band couldn't stand his crappy songs and finally kicked him out.
If you want to drop acid and listen to something mind expanding, prog rock is more likely to do it for you. If, on the other hand, you want to get drunk and just party down, some gritty garage rock or punk rock is the thing. It's the intellectual vs. the soul, and that is why I think prog rock gets the shaft in the Rock Hall. Those making the nominations have traditionally been more of the gritty, soulful variety of rock aficionados. I have an appreciation for both sides, and a lot of stuff in between, so I don't have a problem with acts like Joan Jett and the Blackhearts making their way into the hall, but can certainly see how others feel left out by not having their preferred variety of rock music represented to any reasonable degree.