I can't believe some people are recommending the Sarah Connor Chronicles. The first season was just about watchable despite the horrendous casting, but the second was, aside from Shirley Manson, complete and utter shit. There were a lot of good ideas but it was never coherent and the massive budget reductions meant a painful lack of actual Terminator action. I really like the Cameron character, but that's about it.
Film-wise, onviously the first two are the only great films. 3 is a dreadful movie but the last 10 minutes was brilliant, Salvation again had plenty of good ideas but just never brought them together cohesively. They should have gone with the original idea of Connor being this voice on a radio who only appears at the end, Bale's casting got in the way and just muddled everything up. It was better than T3 though, just in terms of visual design.
The dropped idea of Connor becoming a Terminator was actually not that bad, I always thought it would play nicely with that shot of future John in T2, where he scans the horizon robotically.