I'm not sure what the point of this poll was. I wouldn't say that longplays are "mandatory" for making an educated choice about playing a game, and I didn't see any connection to the thread title.
I find longplays to be extremely helpful when I want to get a general idea of a game without taking the time to download and run it in an emulator, and they help me understand how to get past areas in shoot-em-ups and platformers that have me stumped. In the case of games like Shadow of the Beast II and Brian the Lion, where the game looks and sounds great but isn't fun at all, I just watch the longplay and enjoy the pretty graphics and music. Sometimes, when I'm on a computer that doesn't have an Amiga emulator (any computer that isn't mine), I'll go on YouTube and watch a section or two from a game that I like (this also applies to my non-Amiga games). Finally, they're immeasurably useful when making a tribute video, although my worthless "high speed" Internet connection (76k, courtesy of CenturyTel) has made the extensive downloading required unfeasable for the time being.
In short, I can't see anything bad about longplays at all, or even simple gameplay clips, as long as the quality (both in the video itself and in the player's ability) is good.