These aren't my original ideas, but the person who expressed them to me will not be sharing them anywhere else online. I thought it was a somewhat solid commentary so I wanted to share:
The depth of the original is just not there in this fourth installment. It is ironic that James Cameron couldn't afford to make the original Terminator a post-apocalyptic film as he wanted, but because of this the franchise gets most of the allegiance to its mythology. The fear of the future weighs heavy in the original film. That Sarah Connor is the only one who knows the future brings and is the only one who can do anything about it gives the audience a much stronger protagonist than John Conner in the current film who is already in that future with an army of followers who all know what happened in the past.
None of the time travel paradox is explored in this film. It seems that any scene from the current movie could just be thrown into any action flick and no one would know the difference. It all happens so fast without answering any of the deeper "why?" questions. There is no time to understand or feel a connection with any of the characters because too much stuff is blowing up. I suppose they expected audiences to just worship John Connor because of who he is supposed to be based on previous knowledge.