Why am I posting in VGM's GD, now?
I guess my real question is that is it fair to do so as opposed to whether or not people do it?
Well, fair or not, people judge games by the music, just as people see a movie based on the trailer, or vote for a candidate based on a political ad, or buy gum based on the wrapper.
It is possible that a game won't be as good as its soundtrack, but of course it's also possible that the attention to detail in the music is a sign of the attention to detail in the whole game. The music may only be one element, but it's one of the more important ones, up there with gameplay. It can make a boring, grind-y game compelling (Final Fantasy VIII draw-fests), or relegate a well-made game to obscurity. Just to pick one example out of a thousand, Bio Senshi Dan was a really solid Famicom platformer with lots of upgrades and branching paths, ala Metroid. In terms of graphics, playability, time investment, enemy design, and level design, the two games are basically equal. But one is a legend; one isn't. Why? Bio Senshi Dan didn't have Metroid's soundtrack.
So I don't know that the music is the best way to judge a game. There are hidden classics out there without strong soundtracks. But music is important to the experience, and it seems like as good a starting point as any.
I'm like nothingtosay in that I usually hear a soundtrack and only then get interested in the game. That's why I played Tower of Heaven, Xenogears, Tetris Attack, Metal Gear Solid, and too many others to name. I probably wouldn't have any idea what was going on with video games if I didn't listen to the soundtracks first. The music is also why I replay games knowing that they're crap, but wanting to give them another chance. The music is reason enough to pop in, say, Robocop for the NES one more time.