The Terminator series is a LOOP - T2 fails because of this
T3 tries to fix all the mistakes T2 set. T2 basically says Judgement Day was stopped, and that you can change your destiny. However, this contradicts the superior original movie. The fact that there is a scene with Sarah in the Mexican desert to get her photograph taken is the same photograph Reese has in the future shows that there is NO alterante timelines (like how T2 says) and that Kyle and the Terminator were always a part of May, 1984. Judgement Day was not stopped, and because of this you can skip T2 all together and not miss anything on the story. T3 is the true completion of the Terminator story, and although not perfect, is far superior to T2.
T2 was pretty useless (except for the action). It's just a repeat of the first movie; nothing is accomplished. It just... happens. What T2 should've done was what the third did - how Skynet got power, the start of the nuclear warheads going off, etc. etc. instead of the crappiness that was T2. T3 wasn't a good movie but it at least contributes to the story.