SG-1, compared to many other overdone shows, had one redeeming quality - the protagonists (in this case, all humans) actually progressed through the course of the show. In SG-1 humans went from 1980s level of technology in Season 1 to spaceships, teleporters and off-world colonies in Season 10. So new 'bigger bad' always made some kind of sense, and I feel there was a space for a few seasons worth of additional interesting ideas.
That, or they could have simply continued Stargate: Universe.
There is one series I'm really up in arms about it being recently cancelled - Person of Interest. That one was nowhere close to repetitive, it had tons and tons of space for good, intelligent story developments, and it got cancelled behind the crew's back anyway, because whatever. Fuck you, CBS, for cutting out what was probably the only thing in history of television that approached the topic of AI in a smart, realistic way (and also basically broke Snowden's revelations a year before Snowden).