In the OT, almost every last thing you saw on screen was real, even if it was a minurature or model. It was all stuff you could touch and feel and was really there. In the PT, almost everything you see if CGI, and you can tell it. The PT doesn't feel real at all. Deos Jar-Jar look like someone you could reach out and touch or interact with? No. Does Yoda look nearly as real as he did in ESB? No. In the OT, everything was there. No CGI.
Also, the acting wasn't stale and wooden in the OT, the dialouge was great, and the charecters were real. They were charecters you could really connect with.