I'll definitely consider the separate shows as separate canons. All part of the same continuity but they're pretty distinct casts, so while Universe would be ineligible, SG1 and SGA are definitely old enough.
Since the tie-in novels/comics are by different creators, and significantly less well-known than the tv shows, I'm okay accepting them as separate.
Re: Stargates SG-1 and Atlantis
Since the tie-in novels/comics are by different creators, and significantly less well-known than the tv shows, I'm okay accepting them as separate.