I have always seen Termy and RC to be two completely different franchises (regardless of how much people like to lump them together, I have the same opinions on Alien and Predator) I don't think they can be compared in anyway. and whilst I prefer Robocop I can say that T2 looked better but as Jon said ... thats just Cameron for you, I think its clear with Avatar the guy is more of an effects guy then a story guy.
Terminator 1 was great, and I have to say what I liked about T2 was the effects, but I did enjoy the story. T3 Is not worth mentioning and Terminator Salvation to me felt like a movie some guy had written then some other guy came along and said "Lets add Terminators!!"
Ive said before the next Terminator film doesn't have to be better then Terminator or T2.... it just has to be fun, something the fans can enjoy!