Sorry for rambling about this article on the forums Darren but for whatever reason I can't log in to the site comments sections so I'll put my thoughts on here.
To me, if the original Stargate film had been the only Stargate-related story released up to now...then it wouldn't mean that much to me. It would just be another cool 90s scifi film that I might rewatch every few years.
Furthermore I highly doubt anyone would care enough about it for MGM to want to give it a second look 20 years later. Let's face it, a lot of cool films don't need sequels.
What made the universe come alive was the TV franchise. Yes there are a few people that consider the original movie a classic and not like the TV series but nowadays, when Joe Average thinks of Stargate, they are more likely to think of the TV franchise, probably SG1 to be precise.
In short, the Stargate "product" to use the terms MGM are probably thinking in, owes it's existence more to the TV series than to the original movie. If the TV franchise cannon never happened then for the fans it would be like being thrown into an alternate reality and being expected to believe that the last 20 years didn't happen.
Even for Joe Average, they'd be asking "where's Richard Dean Anderson?" "where's the blonde scientist?" "where's the big guy with the stick?". If you do not reference those characters, even they are going to be confused and your product will fail.
Realistically, any Stargate reboot is going to need to be a "complete" reboot. Forget the movie, forget the TV series. Look at Battlestar Galactica. Last anyone heard from the original series was 1980 right? The new show started up circa 2003. That's the sort of time gap we have to think about.
Last SGU ep was 2011. So MGM shouldn't be seriously thinking about a reboot before some point in the 2030s.
With Star Trek you're comparing apples to oranges. There is an in-story reason for that timeline getting rebooted. Maybe something similar could be done in the Stargate universe but trying to do a reboot without it anytime soon isn't going to work.
Bottom line, the pre-existing TV series are owed some kind of acknowledgement in any future productions.