Theres a whole story out there that puts this film into perspective massively, and the short version is Bale ruined it.
The original script was (apparently) all about a young Kyle Reese befriending a Terminator, and it was about their journey. John Connor was in it only minimally, he is leading the resistance from a sub and rarely comes up for air. He is a voice on the airwaves, a legend/figurehead type thing.
Come the end Connor comes up to see Reese, gets killed, and the terminator ends up taking on the mantle. Sounded like a really interesting idea to me.
Apparently they took it to Bale for the Terminator role, he said "great, I want to be John Connor!" and so the script ended up getting re-written to accommodate him.
It was also on that movie where his infamous tantrum at the sound guy happened, the dingdong.